Running injuries: etiology and recovery-based treatment

Allan Besselink, PT, Dip MDT, and Bridget Clark, PT, MSPT, DPT

An estimated 38 million runners are in the United States, of which 10.5 million are running at least twice a week. Participation in running events (such as a 5K, 10K, or marathon) has increased dramatically in the past 10 years. For example, the number of marathon finishers in the United States has increased from 143,000 in 1980 to 425,000 in 2008. Many health benefits are associated with running, including weight loss, decreased blood pressure, increased bone density, and a decreased risk of both cardiovascular disease and diabetes. These statistics would indicate that running’s growing popularity is a boon to preventative medicine.

However, running also displays a trend toward a significant rate of injury. The current literature indicates various injury rates, depending on the study. Koplan et al. (1982) reported that 60% of all runners will sustain an injury within any given year that is severe enough to force them to alter their training. It has also been reported that the yearly incidence injury rate for runners training for a marathon is as high as 90%. Given that the average runner will have 800 to 2000 footstrikes per mile, the opportunity for injury to occur is significant. Running injuries are not limited to any one joint or anatomic region (Table 7-1), although a large percentage of injuries tend to occur at the knee.

Table 7-1 Incidence of Injuries by Body Area

Data from van Gent RN, Siem D, van Middelkoop M, van Os AG, Bierma-Zeinstra SM, Koes BW. Incidence and determinants of lower extremity running injuries in long distance runners: A systematic review. Br J Sports Med 2007;41:469–480.

These data indicate that running has in fact become a significant health care issue. The number of participants is growing, and a large percentage of those participants will become injured. This suggests a need to better understand the causes of running injuries. Health care providers can then not only provide effective means of treatment should an injury occur, but also provide effective injury prevention programs.

Gait: Walking and Running

The gait cycle has been defined by Thordarson (1997) as the period from initial contact of one foot until the initial contact of that same foot. A brief review of the gait cycle will provide some background on the nature of mechanical loading and the neuromuscular requirements of both walking and running.

Running Mechanics

The walking gait cycle consists of two phases, stance and swing. The stance phase has various components. It begins with initial contact, the moment when the foot contacts the ground. During initial contact, the loading response commences as forces are controlled eccentrically. Midstance starts as the contralateral limb toes off and enters swing phase. Once the center of gravity is directly over the stance foot, terminal stance begins. As the contralateral foot contacts the ground, preswing begins. Stance phase can also be viewed in terms of functional components—the absorption of forces on loading, followed by the propulsion of the body forward. During the swing phase of gait, initial swing begins at toe off and continues until the knee reaches a maximal knee flexion of approximately 60 degrees. Midswing follows and continues until the lower leg/shank is perpendicular to the ground. Terminal swing then proceeds until initial contact is made.

The running gait cycle (Fig. 7-1) is also divided into a stance phase and a swing phase. The stance phase may involve an initial foot contact which takes place as a heel strike, midfoot strike, or forefoot strike. Initial foot contact exists on a continuum with increasing gait speed, progressing from heel strike in walking to forefoot strike in sprinting. The percentage of the gait cycle spent in the stance phase varies depending on gait speed—60% with walking, 40% with running, and just 22% with world class sprinters. The walking gait cycle is distinct in that it involves a period of double limb support in which both of the feet are on the ground. The running gait cycle is distinct in that it involves a period of double float in which both of the feet are off the ground. The progression from walking gait to running gait is a continuum—from double limb support in walking to double float period in running.

Figure 7-1 Normal running gait cycle.

(Redrawn from Mann RA, Coughlin MJ. Surgery of the Foot and Ankle, 6th ed. St. Louis: Mosby, 1993.)

At a certain walking speed, there is a transition from walking to running gait which occurs in order to maintain biomechanical, metabolic, and aerobic efficiency (Fig. 7-2). The speed at which this transition occurs varies between individuals, although it tends to be at or near a velocity of 12:00 per mile (5.0 mph) for most. This becomes an important issue when 70% of the running population runs at a pace of 10:00 per mile or slower. Though fast walking and slow jogging have a similar cardiovascular response, slow jogging creates ground reaction forces and loading rates as much as 65% greater than fast walking (Table 7-2). The progression from walking to running involves certain requirements from the body including the ability to tolerate increased mechanical loads (i.e., ground reaction forces) and the strength not only to progress the body forward concentrically, but also to eccentrically control the stance leg. Running and sprinting require more power and range of motion at the hip, knee, and ankle as speed is increased.

Figure 7-2 Transition from walking to running.

(Redrawn from Besselink A. RunSmart: A Comprehensive Approach to Injury-Free Running, Morrisville, 2008, Lulu Press.)

Table 7-2 Ground Reaction Forces Associated with Walking and Running at Various Speeds

Running Speed	Pace (Per Mile)	Vertical Ground Reaction Force (Body Weight)
1.5 m/s–1 (3.4 mph) (walk)	17:53/mile	1.1–1.5
2.5 to 3.0 m/s–1 (5.6–6.7 mph) (slow jog)	8:56–10:44/mile	2.5
5.0 to 8 m/s–1 (11.2–17.9 mph) (run)	3:21–5:22/mile, or 0:50–1:20/quarter	2.5–2.88

Data adapted from Keller TS, Weisberger AM, Ray JL, Hasan SS, Shiavi RG, Spengler DM. Relationship between vertical ground reaction force and speed during walking, slow jogging, and running. Clin Biomech 1996;11: 253–259 and Munro CF, Miller DI, Fuglevand AJ. Ground reaction forces in running: A reexamination. J Biomech 1987;20:147–155.

During the running gait cycle, the initial functional task of the stance leg is absorption—to eccentrically decelerate and stabilize the limb—before concentrically activating the lower limb for propulsion. The initial phase of stance involves absorbing the ground reaction forces. For walking and slow running up to 3.0m/s⁻¹ (6.7mph, or 8:57/mile), there are two notable peaks in ground reaction forces: the impact peak and the thrust maximum. This two-peaked configuration of the ground reaction curve is consistent in the literature for heel-strike runners. The impact peak occurs during the first 15% to 25% of stance phase. For faster running speeds involving a midfoot or forefoot strike, there is no initial impact peak but usually a single peak, the thrust maximum, and this occurs during the first 40% to 50% of the stance phase.

Ground reaction forces appear to increase linearly up to a gait speed of 60% of maximum speed (average of 4.0m/s⁻¹), but at higher speeds, ground reaction forces appear to stay at approximately 2.5–2.8 times body weight (Table 7-2). It is also noteworthy that during running, athletes that heel strike upon initial contact have a higher initial peak in vertical ground reaction force than midfoot strikers. There is a strong relationship between impact peak and loading rate. The loading rate associated with running has been found to be positively correlated with running velocity, finding an average rate of 77 BW/s⁻¹ (body weight) at slower speeds of 3.0m/s⁻¹, increasing to 113 BW/s⁻¹ at faster speeds of 5.0 m/s⁻¹.

For a runner who has a heel strike, these forces transmit directly through the heel and, therefore, are attenuated by the heel fat pad, pronation of the foot, and primarily passive, more than active, mechanisms in the lower extremity. However, for a runner with a midfoot or forefoot strike, these forces are primarily attenuated by the eccentric activation of the gastrocemius/soleous complex, the quadriceps, and to a lesser degree, the pronation of the foot. Doris Miller, in the book, Biomechanics of Distance Running noted that “initial contact with the heel does not appear to incorporate soft tissue and linked body segment shock absorption mechanisms to as great an extent as landing with initial contact in the midfoot or forefoot region.”

The anterior and posterior calf muscles, quadriceps, hip extensors, and hamstrings all work eccentrically during the stance phase. Of note is the function of the quadriceps, which is the primary shock absorber, absorbing 3.5 times as much energy as it produces. After the initial ground reaction forces are attenuated, the foot then supinates during the propulsion phase to provide a more rigid lever for push off. Winter (1983) noted that the gastrocneminus generates the primary propulsive force during the propulsion phase of running and produces forces between 800–1500 W, compared to 150 W for slow walking and 500 W for fast walking.

The primary purpose of the swing phase is to return the leg back to the stance phase as efficiently as possible. Flexion of the knee shortens the swing limb, effectively reducing the length of the “swinging pendulum”. The hip flexors (including rectus femoris), hamstrings, and ankle dorsiflexors are active both concentrically and eccentrically during the swing phase. There is a small vertical and horizontal translation of the whole body with running. The center of gravity will lower with an increasing velocity of gait. Arm swing is important for balance and for reciprocal running movement, as posterior arm swing corresponds with and assists the propulsive phase of the contralateral limb. The posterior deltoid muscle is very active during posterior arm swing.

Causes of Running Injuries

With the high incidence of running injuries, the suspected factors contributing to injury have been researched for decades. There are virtually as many perceived causes of injury as there are injured runners. A review of the scientific literature would reveal a plethora of perceived causes of and contributing factors to running injury including, but certainly not limited to gender, age, asymmetries and malalignment, leg-length discrepancy, flat feet, high arches, mileage per week, speed work, shoe wear, flexibility (too much or too little), running surfaces (too hard or too soft), gait deviations, history of prior injuries, “muscle imbalances,” training programs, running experience, orthotics, etc.

Review of the current scientific research does in fact yield a definitive answer. One primary factor has been directly associated with the onset of running injury—training or errors in training. James et al. (1978) noted that the primary etiology in two thirds of all causes of injury can be directly related to “training error.” Lysholm and Wiklander (1987) reported that training errors alone, or in combination with other factors, were implicated in injuries in 72% of runners. Simply stated, training error is most often an issue of “too much, too soon,” the importance of which is explained later.

Contrary to the commonly held beliefs of the medical and running communities, there is not any specific correlation between anatomic malalignment or variations in the lower extremity and any specific pathologic entities or predisposition to any “overuse” syndromes. In fact, Reid (1992) noted that “normal variations in the human body abound, and only a few percent of the population are actually good examples of ‘normal.’… Furthermore, all of these variations are found in world class athletes and seem to produce little adverse effect on their ability to perform their sports.… [T]he corollary of this enormous variation of body build among enthusiastic amateur and the professional athletes is that there is a poor correlation of specific malalignments with specific conditions.” Table 7-3 summarizes the sport sciences literature regarding the factors that have been noted to have a direct association with running injury and those that either have no direct association or do not presently have scientific evidence to support an association with running injuries.

Table 7-3 Evidence-Based Factors Associated and Not Associated with Running Injuries

Factors Having a Direct Association with Injury	Factors That Do Not Have Evidence for Association with Injury	Factors Known to Not Have a Direct Association with Injury
“Training error” (most often too much, too soon) Running distance History of prior injury Previous competition in running events	Warmup and stretching exercises Body height Malalignment Muscular imbalance Decreased range of motion Running frequency Level of performance (current skill level) Stability of running shoes Running on one side of the road Orthotics	Gender Age Body mass index Running on hard surfaces Running hills Participation in other sports Time of year Time of day

Data from van Mechelen W. Running injuries. A review of the epidemiological literature. Sports Med 1992;14:320–335.

Training error is the only factor that consistently displays a cause–effect relationship with running injuries. Reid (1992) has gone so far as to state that “every running injury should be viewed as a failure of training technique, even if other contributing factors are subsequently identified.” In addition, running distance of more than 25 to 40 miles per week, previous competition in running events, and a history of prior injury have been found to be strongly associated with running injuries.

There are two types of injuries: traumatic and overuse. A traumatic injury occurs when a single force applied to the tissues exceeds the critical limit of the tissues, such as a collision in football that results in a fractured leg or an ankle sprain while trail running. Overuse injuries occur when repetitive forces are applied to the tissues without allowing the tissues to recover.

Under-Recovery Not Overuse

For years, the health care community has pointed to the “overuse” running injury, but if “overuse” were the problem, then there would be a preset threshold at which point all runners would get injured—and this simply is not the case. Physiologic causes of running injuries can be explained by Wolfe’s law. The body aims to attain homeostasis at the cellular level. As a stimulus is applied to tissues (including bone, tendon, muscle, ligament, and collagen-based tissues), a cellular response is triggered and, over time and with sufficient recovery, an adaptation occurs. This adaptation could be greater tissue integrity, strength, or similar mechanical response. Tissues adapt to mechanical loading if given an environment in which to do so and sufficient metabolic capacity to allow this to occur (Fig. 7-3). This has been shown repeatedly with studies on astronauts and deep sea divers, two populations that face altered repeated and/or sustained mechanical loads. There is a precise balance between stimulus and response—or, for the athlete, the application of a training stimulus and the recovery and adaptation to this stimulus. With this in mind, “overuse” injuries should be more accurately described as “under–recovery” injuries because, given appropriate time for recovery, adaptation to the stimulus will take place successfully.

Figure 7-3 Training stimulus and response. This depicts the body’s ability to recover from and adapt to a single training stimulus.

(Graph originally published in UltraRunning magazine, April 2010.)

Figure 7-3 illustrates the body’s ability to recover from and adapt to a single training stimulus. Figures 7-4 and 7-5 display the effect of several training stimuli: Figure 7-4 with appropriate and sufficient recovery and Figure 7-5 with insufficient recovery and poor training adaptation. Injuries occur when the rate of application of training stimulus exceeds the rate of recovery and adaptation.

Figure 7-4 Repeated training stimuli and responses, given appropriate and sufficient recovery. This depicts the body’s ability to recover from and adapt to repeated training stimuli successfully.

(Graph originally published in UltraRunning magazine, April 2010.)

Figure 7-5 Repeated training stimuli and responses, given insufficient recovery and poor training adaptation. This depicts the body’s inability to recover from and adapt to repeated training stimuli when insufficient recovery time and poor training adaptations occur.

(Graph originally published in UltraRunning magazine, April 2010.)

The rate of recurrence of running injuries is as high as 70%. There is little scientific evidence to relate any specific biomechanical factors to the onset of these injuries, yet upward of 70% of running injuries have been found to be related to training errors alone. It becomes imperative for the clinician to understand the relationship between training stimulus and training recovery and adaptation, keeping in mind that the human body is well-adapted to respond to the demands required for running. Assessment and treatment should focus on the training error that disrupted the normal adaptation process. Using this information, the clinician can create an environment that promotes healing and builds the capacity to tolerate the demands of running.

A Problem: Our Perception of Running Injuries

Run training and the assessment and treatment of running-related injuries are at a crossroads. Assessment and treatment efforts have focused on biomechanical malalignments and the like, yet we now have 30+ years of sports science research that indicates that the primary issue related to the onset of running injuries is training error. Although the scientific evidence exists, the application of it has been absent or misguided clinically. Perceptually, there has been a quantum leap between perceived causes and treatments, a leap that is simply unsubstantiated in the scientific literature. With this in mind, it becomes readily apparent that health care providers need to understand training demands to effectively and optimally address the problems of the injured runner. Instead of simply being a case of “overuse,” most running injuries will in fact be an issue of “under-recovery” or impaired adaptation. It is the body’s inability to adapt to the imposed demands of training, which is most commonly an error in the training program. Simply put, if training is the problem, then training is the solution.

Assessment must focus not on the isolation of the perceived specific biomechanical malalignment, but on the (a) understanding of the mechanical dynamics leading to injury, and (b) dynamics of the training program. Treatment then focuses on a graded “return-to-training” progression, given the basic rules of tissue repair and remodeling.

Mechanical Assessment

Subjective

A thorough examination should begin with a review of the patient’s prior running program. We have compiled a list of characteristic traits of the run training program that typically contribute to factors related to overuse/under-recovery (Table 7-4). This assists the clinician’s understanding of the athlete’s current capacity to tolerate mechanical loading. The intent and rationale for each question has also been provided.

Table 7-4 Run Training History

Running Experience	Intent/Rationale of Question
1. Have you been involved in any other sport or fitness activities, and if so, for how long?	General level of conditioning and tissue “health” and current loading capacity.
2. How long have you been a runner?	More experienced runners tend toward lower injury risk.
3. Have you had any previous running injuries? If so, where and when?	Injury risk increases if history of a prior running injury.
Current Training Program	Intent/Rationale of Question
1. How many days per week do you run?	Number of recovery days per week.
2. How many miles do you run per week?	Most programs emphasize “more is better”; injury risk tends to increase at 25–40 miles per week
3. What is your average running pace (minutes/mile)?	Running mechanics change with running pace.
4. What was your longest run in the month prior to injury?	The rate of progression of the total volume of training and loading capacity.
5. Do you recall any change in your running program that occurred just prior to the onset of your injury?	Injured runners most typically have some type of sudden change in the volume of their training; the rate of application of training stimuli exceeds the rate of adaptation to training.
6. Are you training with a group or individually? Are you using a published program or a coach?	Access to the program itself can be valuable for further analysis by the clinician (see #5).
7. What is the longest run that you have done since you noted the injury? How long ago was this done?	Allows the clinician to better understand where to resume running when the athlete is ready (i.e., longer break = more gradual resumption of training).
8. Do you compete in races? If so, what distance(s)? Are you currently training for a particular event?	Injury risk is higher in those who have competed in the past. If they are currently training for an event, it may affect their rate of progression and return to running, along with their overall goal setting.
9. Do you do interval training (speed work) in your training program? If so, what and how often?	Is the athlete doing any run training activities that are building power and loading capacity?
10. Do you do strength and/or plyometric training as part of your training program? If so, what exercises are you doing? Typical number of sets and repetitions? Light, moderate, or heavy resistance? Number of days per week?	Strength and plyometric training (high load, low repetitions) build greater loading capacity and power output.
11. Is there anything else you would like to tell me about your running program?	It is common that the athlete will have an inherent “sense” of the factors that contributed to the injury. Ask them!

Objective

Care of the athlete has many approaches. Establishing a mechanical cause and effect is integral in effectively diagnosing and treating the athletic population. A reliable and valid assessment and clinical reasoning process—for the injured runner and the orthopaedic patient in general—would entail some form of mechanical evaluation. The primary goal of any assessment process is to utilize reliable and valid procedures; however, review of the scientific literature to date indicates that many currently used assessment procedures—including palpation-based methods of assessment—are not only unreliable, but also have questionable validity in the clinical reasoning process. Research does, however, support the use of provocation- and movement-based testing procedures.

The McKenzie method of Mechanical Diagnosis and Therapy, or MDT™ (The McKenzie Institute, Syracuse, NY), forms the basis of the mechanical assessment and is presented here because it is a comprehensive classification and treatment system that has scientific research to support not only its assessment process, but also its classification algorithm. Although MDT™ initially gained widespread international acceptance for the treatment of spinal pain, its principles also are readily applied to the extremities. Three primary aspects are unique to the McKenzie method™—mechanical assessment, self-treatment, and prevention (Table 7-5). Although a complete description of the McKenzie method™ is not within the scope of this chapter, further resources can be found in the reference list at the end of this chapter.

Table 7-5 Basic Concepts of Mechanical Diagnosis and Therapy™

Mechanical Assessment

1. Establish a relationship between symptom response and mechanical loading (typically via repeated test movements). 2. Systematically apply progressive mechanical loading strategies. 3. Use reliable classification system that leads naturally to treatment and patient self-care .

Self-treatment

1. Provide patients with the necessary knowledge and tools to treat themselves.

2. Decrease reliance on clinician.

3. Empower patient to become self responsible

.

Prevention

1. Provide patients with the knowledge of what to do if problem reoccurs.

2. Develop patient understanding of cause of problem to know how to prevent problems in the future

.

The mechanical therapist seeks to understand the effect of a systematic progression of mechanical forces and loading strategies (and the symptomatic and functional responses to these strategies) to diagnose and treat conditions of the musculoskeletal system. Mechanical loading strategies include the use of static sustained positions and dynamic repeated movements. This helps to establish a cause and effect between mechanical loading and symptom response. The MDT™ classification uses a well-defined algorithm and provides a reproducible means of separating patients with apparently similar presentations into definable subgroups (syndromes) to determine appropriate treatment interventions. It is not so much a “treatment technique” as it is a “process of thinking.” Research has shown the initial MDT™ assessment procedures to be as reliable as costly diagnostic imaging (i.e., magnetic resonance imaging [MRI]) to determine the source of the problem. The assessment process quickly establishes responders and nonresponders with classification guiding the treatment intervention.

MDT™ fits well within a sports medicine paradigm given that training will involve many hours of repetitive mechanical loading. Add to this axial loading (i.e., that which occurs with ground reaction forces) and you have the potential for mechanical disorders related to sustained positioning and/or repetitive mechanical loading while running. The mechanical assessment process is clinical reasoning based on sound mechanical principles.

Other sport-specific functional mechanical tests can be used to allow the clinician to further assess the athlete’s dynamic eccentric loading capacity and neuromuscular control. Running injuries are typically a problem of eccentric loading and weightbearing; thus functional mechanical tests should incorporate similar types of loading, including strength and plyometric testing. The functional tests can be simple and are again directly related to treatment. For example, knee hops (hopping motions using ankles and knees) and ankle hops (hopping motions with the knee locked) can be used with a graded progression of loading. The progression would be two-legged hops (for vertical), to one-legged hops (for vertical), to two-legged hops (for horizontal), to one-legged hops (for horizontal). Reproduction of concordant symptoms (or lack thereof) is key. This uses the principle of “hurt, not harm” in which loading may reproduce the symptoms during the activity, but the symptoms are not increasing and do not remain worse afterward, indicating that the affected tissues are being loaded appropriately.

Gait assessment is also considered a functional mechanical test and serves two primary purposes. It is a benchmark for the athlete’s current movement pattern and provides the foundation for running form development. It also provides insight into the athlete’s ability to tolerate eccentric loading and, combined with his or her running/injury history, provides a more complete understanding of the potential training factors related to the onset of the injury.

Education

Education of the patient is a critical element in the effective treatment of the injured runner.

MDT™ uniquely emphasizes education and active patient involvement in the management of their treatment, which minimizes the number of visits to the clinic. Ultimately, most patients can successfully treat themselves when provided with the necessary knowledge and tools. Active approaches to care enhance patient self-responsibility, and education and empowerment of the individual become integral to effectively dealing with injury and the further goal of injury prevention. By learning how to self-treat the current problem, patients gain hands-on knowledge on how to minimize the risk of recurrence and to rapidly deal with recurrences.

The goal of the assessment process is to establish movements, positions, and exercises that will allow the patient to self-treat, if an injury responds successfully to a certain direction of movement. Self-care strategies can be used so that the athlete can be applying mechanical loads to the affected tissues on a regular and consistent basis to promote reduction of the mechanical problem (directional preference) or to stimulate tissue repair and remodeling. The athlete needs to be aware of how to apply safe and appropriate mechanical loads and how (and when) to progress them. By doing so, the athlete can be applying the right forces at the right frequency, far more effectively than a two- or three-times-per week clinical treatment approach. In this way, the practitioner becomes the “guide” and the patient takes an active role in implementing the prescribed treatment with increasing independence. This refines the role of the clinician in the health care spectrum—to one of problem solver, educator, and mentor.

As the patient recovers from injury and returns to running, the physical therapist thoroughly reviews the progression back to running to prevent reinjury (see Table 7-4). Runners, like most athletes, are eager to return to athletic training and competition. Because running injuries are generally training related, it is imperative that athletes understand how to modify their training to foster injury recovery and tissue repair, how to prepare their body to accept the increasing mechanical loads with running, and how to optimize their performance. Most runners are under the mindset that “more is better.” Because research clearly dictates otherwise for runners, it is imperative to educate the patient.

Progression of the program is based on appropriate symptomatic, functional, and mechanical responses to loading. Based on this loading response, the athlete is given the green light to progress the functional loading within his or her training program. Having knowledge of this allows the athlete to progress steadily within the timeline and limits of normal tissue repair, and under his or her own control.

Building Capacity

Principles of Optimal Run Training

The training plan is essential to review, discuss, and modify if necessary as an integral part of the treatment plan. The following training principles should assist the clinician in making good recommendations for the running athlete (Table 7-6).

Table 7-6 Optimal Training Principles for Runners

Adapted from Besselink A. RunSmart: A Comprehensive Approach to Injury-Free Running. Raleigh, NC: Lulu Publishing, 2008.

Evidence suggests that an arbitrary 10% increase in weekly mileage is not effective at reducing running-related injuries because 7 days may not be long enough for the body to adapt to increased repeated loading. Because of this and evidence to support that recovery from an increased run distance takes 10 to 14 days, we recommend a progression of loading based on the current level of training adaptations (Table 7-6). Table 7-6 is not a comprehensive list, but it does include the primary elements of an optimal and effective training program.

Much like any other sport, improving running biomechanics will help improve efficiency over the long term. The feedback of a professional coach can be exceedingly useful in improving a person’s running mechanics. At the time of this publication, a number of running philosophies are targeted at this subject, including Chi Running,™ POSE Method,™ RunSmart,™ and Evolution™ running, among many others. Most propose similar premises regarding running form but use different cues and strategies to attain it and varying levels of training-related information to support it. Running injuries are not simply a “running form error”; education regarding recovery-based training is critical to developing an optimal and safe training program.

Clinical Case Study

Bob is a 40-year-old male with a 5-year history of running. He runs 4 to 5 days/week at a 10:00/mile pace. He complains of left lateral knee pain of gradual onset 3 weeks ago. Two weeks prior to the knee pain, he increased his daily mileage from 5 miles to 8 miles and started running 6 days/week. He had previously been running 4 days/week. He cannot run more than 1 mile without increasing pain and notices the pain with going up and down steps. His goal is to return to pain-free running and train for a half marathon.

The mechanical assessment of the patient reveals that a single-leg squat reproduces the pain and this pain worsens with repetitions. Pain is also produced with one leg hopping (10 times), but only after the fifth repetition. These activities can be used as functional benchmarks during the assessment process. Knee ROM is full; however, there is pain reported at the end range of knee extension. This is also used as a benchmark.

The patient is then asked to perform repeated movements to assess their effect on these benchmark activities. The patient is asked to perform repeated knee flexion 30 times to end range, and the benchmarks (ROM, single-leg squat, hopping) are reassessed. This patient’s pain is worse with both activities and begins at an even earlier repetition. The same process is repeated with knee extension. His pain is 50% better with functional tests, and knee ROM is now full and pain free.

From the perspective of the mechanical assessment, the patient now has a directional preference with a preferred mechanical loading strategy—knee extension—which displays a lasting favorable response symptomatically, mechanically, and functionally. The clinician prescribes the knee extension (with gentle overpressure) exercise to the patient four to six times/day and at any time he should have concordant symptoms. This gives the patient control over his self-care.

Based on the history, some hallmark issues in the training program can be addressed. Although Bob is an experienced runner, he was unable to adapt to the increased load and increased load frequency placed on his body, thus resulting in an injury (see Fig. 7-5).

On followup, Bob reports a 50% overall improvement. He has not tried running, but all daily activities are pain free. He reports that if he does experience symptoms or any knee stiffness, the exercise (knee extension with gentle overpressure) abolishes them. He is instructed in a lower extremity strength and plyometric training program, which he tolerates with minimal awareness of the knee (that is abolished with repeated knee extension). At this point, he is instructed to resume running after the first 2 to 3 days of strength training as long as it does not increase lasting knee pain and to stop and use the extension exercise to reduce knee pain while running, if necessary. He is advised to resume interval training with a 1-minute walk/1-minute run strategy for a total of 20 minutes. When he achieves this, he can then progress to 30 minutes total. Followup with the clinician is scheduled for after the patient’s 30-minute walk/run.

Bob returns to the clinic for visit 3, having been able to do the 30-minute walk/run without complaints. He is told that this is typically a good benchmark for the return to continuous running; however, instruction regarding his training program is required. Bob is provided with some guidance regarding a safe and effective run training program, reducing the frequency of running to 3 to 4 days/week; of this, 2 days per week would be interval based. He would have 2 recovery days per week; strength training (one set of 10 almost maximal weight) could be performed on his recovery days. His longest run would increase every second week, not every week as he had been doing (because it takes the musculoskeletal system 10 to 14 days to recover from the long run).

Bob returns to the clinic 2 weeks later and reports 90% improvement. He has been doing the prescribed home exercise program and following the “hurt, not harm” principle. He reports he can run now 3 miles without pain and up to 4 miles with slight pain that resolves with the prescribed knee exercise and has no pain immediately after running. Bob is eager to resume his half marathon training. The clinician is pleased with the progress and educates Bob on training principles to progress appropriately and prevent reinjury. With the help of the clinician, Bob develops a training plan that incorporates appropriate rest days, interval (speed) training, strengthening, and training volume progression based on the time required for adaptation to loading.

Summary

Lessons learned from running injuries have a significant impact on our perception of the role of rehabilitation and self-care strategies on all orthopedic and musculoskeletal conditions. It is imperative to look to the training program for both the cause and the solution for running injuries. The patient needs to play the most important role in their recovery for successful recovery and prevention of injury re-occurrence. Education may be the most valuable treatment the clinician can provide.

Running injuries: shoes, orthotics, and return-to-running program

Scott T. Miller, PT, MS, SCS, CSCS, and Janice K. Loudon, PT, PhD

The running stride is divided into an active and passive absorption phase and a generation phase (see Fig. 7-1). The purpose of the active absorption phase is initially to decelerate the rapidly forward-swinging recovery leg with eccentric hamstring activity, first absorbing and then transferring the energy to the extending hip, placing the hamstrings under considerable stress. Passive absorption begins at footstrike with absorption of the shock of ground reaction force resulting in a force 2.5 to 3 times body weight (BW) and up to 10 times BW running downhill. This initial shock is attenuated by the surface, the shoe, and the heel pad but not to a great extent. Subsequently, the ground reaction force is actively absorbed by muscles and tendons as it increases to midsupport with a relative shortening of the extremity. This is accomplished by hip and knee flexion, ankle dorsiflexion, and subtalar pronation accompanied by eccentric contraction of the hip abductors, quadriceps, and gastroc–soleus muscles along with stretching of the quadriceps and patellar tendon, Achilles tendon, and plantar fascia. At this point, the ground reaction force with running may be as much as five times BW. The stretched tendons absorb energy, store it as potential energy, and then return 90% of it later in the generation or propulsive phase as kinetic energy, with the remaining 10% creating heat in the tendon.

During the generation phase in the second half of support, there is a relative lengthening of the extremity with concentric muscle contraction and joint extension, with return of stored potential energy as kinetic energy from the tendons significantly assisting the now concentrically contracting muscles. Peak forces maximize at the sites of chronic injury (Scott and Winter 1990). Forces in the patellofemoral joint estimated at 7 to 11.1 times BW, 4.7 to 6.9 times BW in the patellar tendon, 6 to 8 times BW in the Achilles tendon, and 1.3 to 2.9 times BW in the plantar fascia predispose the tissues to potential injury from repetitive overuse—particularly if combined with even a minor anatomic or functional variation.

Examination of the entire lower extremity thus becomes essential (Fig. 7-6) when the extremity is viewed as a kinetic chain whose normal function is dependent on the proper sequential function of each segment. Therefore, concentrating on only the area of complaint may overlook the underlying cause of the problem (e.g., anterior knee pain related to compensatory foot pronation and imbalances in proximal stabilizers).

Figure 7-6 Runner’s encounter form.

The examination evaluates the following (Fig. 7-7):

Figure 7-7 Runner’s examination sheet.

A basic two-dimensional video analysis of the runner’s gait can be accomplished with an inexpensive camcorder setup or utilizing more advanced video management software (Dartfish) with multiple high-speed camcorders in the office.

Shoes

It is evident that the etiology of overuse running injuries is a multifactorial problem and successful management often relies on sound decision making by the clinician. One key factor is the consideration of matching the appropriate footwear to an individual’s foot classification, including alignment, mobility, and biomechanical factors related to running. Clinically, footwear recommendations are a necessary compliment to the various treatment approaches for running injuries.

To provide appropriate recommendations on running footwear, having a basic understanding of how the shoe is constructed is important. The key features of a running shoe include the outsole, midsole, and upper. The outsole is the bottom of the shoe and is generally made from carbon or blown rubber. The midsole is the shock-absorbing layer between the outsole and the “upper” part of the shoe. This midsole is the most important part of a running shoe because the construction and materials used will affect the levels of both cushioning and stability in the shoe. The amount of cushioning in the shoe is generally proportionate to the shoe’s heel height. The two types of cushioning generally found in running shoes are ethylene vinyl acetate (EVA) and polyurethane (PU). Increased stability in a shoe is accomplished through the incorporation of a heavier density EVA or PU in combination with the existing cushioning materials. This type of construction is referred to as a dual-density midsole. Finally, the “upper” is the soft body of the shoe that encloses the foot and is usually made of a combination of materials, from lightweight, durable synthetic mesh to heavier materials such as leather. The materials and construction of the upper provide stability, comfort, and a snug fit. Features to consider in the upper include the last (the shape of the shoe), the toe box (the front of the shoe), the heel counter (the part holding the heel, which can vary in stiffness for increased stability), and the Achilles notch (a groove in the heel piece to protect the tendon from irritation). Running footwear can be divided into four primary categories related to their overall cushioning and stability properties (Table 7-9): (1) light cushion, (2) straight last cushion, (3) stability, and (4) motion control.

Table 7-9 Classifications and Characteristics of Running Shoe Types

* Board last construction primarily used with older running shoes and basketball shoes. Combination last primarily used now in newer running shoes.

Source: Gazelle Sports, Grand Rapids, MI, and Agility Physical Therapy & Sports Performance, Portage, MI.

A light cushion running shoe (Fig. 7-8A) is best for a true supinatory foot or for someone who is an underpronator. This foot type is generally fairly rigid in nature with pes cavus presentation; thus it does not absorb shock during the initial contact phase of running. A light cushion running shoe is not a very substantial shoe and is constructed of single-density material for the midsole with minimal arch support. This shoe is extremely flexible through the arch to allow the foot as much motion as possible. In general, a light cushion shoe will break down quickly (typically less than 400 miles/643 km).

Figure 7-8 Running shoe categories. Light cushion (A), straight last cushion (B), stability (C), and motion control (D).

A straight last cushion running shoe (Fig. 7-8B) is a newer category shoe, described as a hybrid shoe that is a transition between a light cushion and stability (described next) shoe. This type of shoe is best for someone who is an underpronator but still presents with some of the forefoot and/or rearfoot alignment concerns (e.g., forefoot varus or calcaneal varus). This foot type is generally somewhat rigid but more accurately does not have the necessary motion available at the subtalar joint to accommodate for the positional faults (e.g., uncompensated forefoot varus). This unique shoe still uses the single-density cushioning material for the midsole, while providing more inherent stability based on the geometry of the shoe (straight last construction) versus implementing a dual-density midsole or stability system commonly seen in the stability shoes. Clinically, this shoe provides a more stable platform for the foot and/or foot orthosis to function without the extrinsic influence of the shoe, which may or may not be desirable.

A stability running shoe (Fig. 7-8C) is best for someone who is a mild to moderate overpronator. This type of shoe generally has enough mobility in the subtalar joint to assist in shock absorption during stance phase. This shoe encompasses some additional stability through the midsole with some type of added stability feature like a dual-density material found in most brands or the Graphite Rollbar system found exclusively in the New Balance shoes. A stability shoe does allow for some flexibility through the midfoot, but it has enough rigidity to provide pronation control.

Finally, a motion control shoe (Fig. 7-8D) is designed for the moderate to severe overpronator. This foot type generally has the same forefoot and rearfoot alignment concerns, but by stark contrast to the more rigid foot, it has an excessive amount of subtalar and/or midtarsal joint motion available. A foot type that can compensate for a forefoot or calcaneal varus can present dynamically as an overpronator (at midsupport) or as a late pronator (at take-off). This causes the foot to roll inward, placing excessive stress on soft tissue structures proximal to the foot, including the lower leg, knee, hip, and back. Motion control shoes are straight-lasted, have a very broad base for support, and are constructed of either a dual-density midsole or a Graphite Rollbar system. This shoe is very rigid through the midsole, much more than the stability shoe, to provide maximum pronation control.

When making footwear recommendations, several factors that can influence the type of shoe ideal for each individual runner must be considered. It is imperative that the individual’s foot type matches the shoe by evaluating whether the runner has a flexible or rigid foot type. Next, consider whether the runner has an overall neutral, varus, or valgus alignment. A clinically challenging foot to manage is in the runner who has a forefoot varus combined with a rigid foot type. Furthermore, overstabilizing the foot can be just as detrimental to the soft tissue structures of the lower extremity as understabilizing the foot. Finally, for an individual who has significantly different foot types (e.g., left foot = supinatory foot; right foot = overpronator), the best clinical decision may be to understabilize the foot (e.g., straight-last cushion shoe) and selectively increase the stability with a customized foot orthosis.

Other factors to take into consideration include

Much emphasis has been placed on the role of shoes in shock absorption at footstrike, and shoes are of some benefit but provide little, if any, force attenuation when the forces are maximal at midsupport or during push-off. This does not mean shoes are of no importance in protecting the runner, but perhaps realizing their limitations is critical in injury management. For example, if a runner has been identified as having a late-pronation problem dynamically, in most cases, a customized foot orthosis with posting extending medially into the forefoot may be indicated. The overall goal with any shoe or shoe–orthosis combination is to provide the optimal biomechanical balance from the foot proximally to the pelvis.

Inspection of a runner’s shoes that have been worn a while for excessive wear or distortion, including the midsole, heel wedge, heel counters, or midfoot, can provide useful information.

Orthotics

The use of a foot orthosis (commonly referred to as an “orthotic”) to address lower extremity overuse running injuries by controlling foot abnormalities has been recommended by various health care professionals for years. Despite the disagreement in the literature as to what type of foot orthosis is superior (e.g., rigid vs. semiflexible; full-length), successful treatment with the use of orthotics is dependent on careful evaluation of the runner and formulation of a properly fitted device. Several advantages and disadvantages of each device need to be factored into the decision making process. The normal foot functions most efficiently when no deformities are present that predispose it to injury or exacerbation of existing injuries. However, in many cases, when a lower limb overuse injury is present, lower extremity extrinsic or primary foot abnormalities are present. An orthosis can be used to control abnormal compensatory movements of the foot by “bringing the floor to the foot.” This will allow the foot to function more efficiently in a subtalar joint neutral position and provide the necessary support so that the foot does not have to move abnormally.

When making a clinical decision regarding the type of device to use, it is important to have an understanding of how the device is to function. There are basically two types of orthoses:

• A biomechanical orthosis is a hard device (Fig. 7-9A) or semi-flexible device (Fig. 7-9B) capable of controlling movement-related pathology by attempting to guide the foot into functioning at or near subtalar joint neutral. This device consists of a shell (or module) that is either rigid or flexible with noncompressible posting (wedges) that are angled in degrees on the medial or lateral side of the foot that will address both forefoot and rearfoot deformities. The rigid-style shell is fabricated from carbon graphite, acrylic Rohadur, or (polyethylene) hard plastic. The control acquired is high, whereas shock absorption is sacrificed somewhat. The flexible shell is fabricated from thermoplastic, rubber, or leather and is the preferred device for the more active or sports-specific patient. The semi-rigid device takes advantage of various types of materials that provide both shock absorption and motion control under increased loading, while retaining their original shape. The rigid devices take the opposite approach and are designed to firmly restrain foot motion and alter its position with nonyielding materials. Both the rigid and flexible shells are molded from a neutral cast and allow control for most overuse symptoms.

• An accommodative orthosis is a device that does not attempt to establish foot function around the subtalar neutral position but instead allows the foot to compensate. These devices are designed for patients who are deemed to be poor candidates for biomechanical control as a result of congenital malformations, restricted motions in the foot or leg, neuromuscular dysfunctions, insensitive feet, illness, or physiologic old age. The materials used to fabricate the shell will yield to foot forces rather than resist them. Compressible wedges are used to conservatively bias the foot into a more varus or valgus position depending on the desired direction.

Figure 7-9 Biomechanical orthoses. Rigid, sulcus-length device (A), semi-flexible, full-length device (B), and semi-flexible, full-length device with rearfoot to forefoot medial posting (C).

When specifically dealing with runners, a semi-flexible, full-length device using extrinsic posting on a neutral shell (Fig. 7-9C) is recommended for several clinical reasons. First, the functions of the foot during the gait cycle are adaptation, shock absorption, rigid support for leverage, and torque conversion. More specifically, at footstrike, the foot acts as a shock absorber to the impact forces and then adapts to the uneven surfaces. If the prescribed device is rigid (e.g., carbon fiber), this rigidity creates the potential for decreased shock absorption by the device attenuated through the soft tissue structures and less ability for the foot to adapt to the surface. Furthermore, at take-off, the foot has to return to a rigid lever to transmit the explosive force from the lower extremity to the running surface. If primary abnormalities of the foot are related to the forefoot (e.g., forefoot varus), consideration needs to be given to correcting this alignment issue with a full-length device to assist in the transition back to a rigid foot from a supple foot. Finally, most researchers will concur that the use of orthotic therapy is both a “science and an art.” There are advantages to using extrinsically posted, neutral module devices (versus intrinsically designed modules) such as ease of modifications or adjustments. With extrinsically posted devices, different types and density of materials can be selected for support and posting. For example, felt, cork, and EVA are common supportive or posting materials used for this type of orthosis. There is also variability in the stiffness (durometer) rating of such materials as EVA depending on the desired function of the material or the weight of the patient.

Regardless of the clinician’s philosophy regarding orthotic therapy or the type of orthosis that is used, the goal is to create biomechanical balance at the foot that will subsequently influence the proximal kinetic chain the patient will wear. A device that is uncomfortable or painful is undesirable and will be detrimental to the overall rehabilitation process.

Foot orthotics should be considered for any lower extremity overuse syndrome related to runners, not just the obvious diagnoses of plantar fasciitis or medial tibial stress syndrome. Often a trial with a less expensive over-the-counter (OTC) insert to see whether there is a benefit may be a reasonable approach before prescribing a more expensive custom orthosis. A semi-custom foot orthotic can be fabricated by attaching different density materials to the underside of the OTC device. This may be a cost-effective solution, especially for younger, still-growing runners, to achieve the desired outcome. When prescribing a custom foot orthotic, it is mandatory to understand and fulfill the fabricator’s requests for measurements and cast molds. Selecting an orthotics laboratory that has the same philosophical approach to managing foot biomechanics is critical. A poorly fabricated orthotic is a waste of the patient’s time and money.

Physical Therapy and Rehabilitation

The treatment of runners must be a coordinated effort on the part of the physician, physical therapist, athletic trainer, coach, parent, and runner.

The goal of a rehabilitation program for runners after injury or surgery is restoration of flexibility, ROM, muscle strength, balance, motor control, and endurance of the entire lower extremity with return to uninterrupted running.

As a general rule, closed chain exercise including concentric and eccentric muscle activity is preferable for runners. Although a good starting point in some cases, isolated, concentric, open chain exercises may induce strength changes in ROM not present during running and create the potential for muscle imbalance. Specific rehabilitation regimens for a given condition are covered in several different sections in this book specific to the condition. Overall, the goal is to develop a functionally based exercise program that will correct any imbalances in the neuromusculoskeletal system. See Table 7-10 for an overview of running injuries and corresponding treatment strategies.

Table 7-10 Running Injuries and Treatment Strategy

Stretching for flexibility (Figs. 7-10 and 7-11) should be an integral part not only of a rehabilitation program, but also of the daily training program (see each section). Although important for all runners regardless of age, stretching becomes even more significant with aging as tendons become less extensible and joints tend to lose flexibility. Furthermore, isolated tightness can cause muscle inhibition, as described by Janda (1983, 1985). One example is the concept of lower cross syndrome, which is the reciprocal inhibition of the gluteus maximus resulting from iliopsoas tightness. This is a common presentation with runners who have recalcitrant hamstring strains or chronic low back pain. If the iliopsoas tightness is not corrected, the likelihood of retraining the proper gluteus maximus firing pattern is reduced.

Figure 7-10 Runner’s flexibility program.

Figure 7-11 Iliotibial band (ITB) stretching program.

(Modified from Lutter LD. Form used in Physical Therapy Department at St. Anthony Orthopaedic Clinic and University of Minnesota, St. Paul, MN.)

The vague complaint of the extremity “not feeling right” may be a result of muscle imbalance secondary to either weakness or contracture. It is imperative to evaluate both the flexibility and endurance strength to determine potential risk factors. For example, regardless of the cause, runners presenting with hamstring and gastrocnemius–soleus muscle contractures or weakness resulting in recurrent or chronic muscle/tendon strains can develop alterations in stride, predisposing tissues to excessive stress.

A functional rehabilitation program should be designed to simulate, as close as possible, the normal muscle and joint function of running. Often, so much emphasis is placed on the injured area that the rest of the body is ignored. It is critical to think above and below the affected area (e.g., diagnosis of iliotibial band friction syndrome, evaluation of the foot and hip). Total body fitness and cross-training techniques, such as running in water with an AquaJogger® (Excel Sports Science, Inc., Springfield, OR), can be beneficial in maintaining overall cardiovascular and muscular endurance while tissue healing takes place.

Once the runner is ready to return to running after missing training, the following guidelines may be helpful. If left to their own judgment, most will return too fast, resulting in either delayed recovery or reinjury.

Return to Running Algorithm 2 (Miller’s Recommendations)

The following return to running programs should be considered a “guide” for return to running after a significant absence from training of 4 weeks or more as a result of injury or surgery. The four different return-to-running programs are designed to meet the needs of the individual runner and the type of injury involved.

The purpose of any return-to-running program is to condition the musculoskeletal system; it is not intended to be a significant aerobic conditioning program, which can be accomplished with low or no-impact cross-training. Generally, the running pace should be no faster than 7 minutes per mile and the walking should be done briskly. The program is based on time, not distance. Rest days should be scheduled every 7 to 10 days or as indicated. The schedule can be varied to meet individual situations. If need be, the runner may hold at a given level longer, drop back a level, or, in some instances, skip a level if progressing well. Generally, if the runner’s “original symptoms” return during a workout, then the runner should be instructed to return to the previous “successful” workout before trying to advance any further. Discomfort may be experienced, but it should be transient and not accumulate or create any gait deviations (e.g., limping).

Summary

It is important to incorporate general strength training, specific prescribed rehabilitation exercises (e.g., neuromuscular re-education), and/or stretching program with the return-to-running program. A comprehensive evaluation of the individual plays a vital role in the appropriate management and successful outcomes. This requires looking proximal and distal to the affected area or joint. Performing some type of videotaped gait analysis (Table 7-11) is critical in being able to accurately determine running form aberrances (e.g., heavy slapping asymmetric heel strike) and prescribe the necessary footwear changes or the need for a customized foot orthotic. Finally, a functional exercise program and appropriate return-to-running progression will provide the individual with the greatest opportunity for a successful return and to accomplish their personal goals.

Table 7-11 Video Running Analysis Form (Gait Laboratory)

Groin pain

Michael P. Reiman, PT, DPT, OCS, SCS, ATC, FAAOMPT, CSCS, and S. Brent Brotzman, MD

Background

Groin pain is a broad, general term that means different things to different people. Patients may describe “I pulled my groin” (groin strain), or “I got kicked in the groin” (testicle), or “I have a lump in my groin” (lower abdominal wall). It is estimated that 5% to 18% of athletes experience activity-restricting groin pain. This groin pain is common in sports involving repetitive kicking, twisting, or turning at high speeds. The complex anatomy and multitude of differential diagnoses make the identification of a specific cause difficult, as do the often diffuse, insidious, and nonspecific symptoms. Adding to the diagnostic dilemma is the fact that two or more injuries may coexist. The keys to this diagnostically challenging problem are thorough history taking and examination.

Initially it is important to establish accurately whether this is an acute injury (usually musculoskeletal) or a chronic symptom (often nonmusculoskeletal in origin). Second, the correct anatomic area being described should be identified (e.g., hip adductors [medial], hip, testicle, lower abdominal wall). The commonly accepted definition of a groin strain focuses on injury to the hip adductors and includes the iliopsoas, rectus femoris, and sartorius musculotendinous units (Fig. 7-12). An accurate area of anatomic pain must be delineated by the examiner (e.g., adductor origin or testicular pain with radiation).

Figure 7-12 Among the musculotendinous injuries of the thigh that can cause groin pain, adductor longus muscle injuries are the most common. Any injury to the iliopsoas, rectus femoris, sartorius, or gracilis muscle can also produce groin pain.

(Redrawn from DeLee JC, Drez D Jr, Orthopaedic Sports Medicine: Principles and Practice. Philadelphia: WB Saunders, 1994.)

In a study of 207 athletes with groin pain (Hölmich 2007), adductor-related dysfunction was the primary clinical entity (58%), followed by iliopsoas-related dysfunction (36%) and rectus abdominus–related dysfunction (6%). Multiple clinical entities were found in 33%.