Anterior Cruciate Ligament Injuries

The anterior cruciate ligament (ACL) primarily resists anterior tibial translation on the femur; it also prevents hyperextension and extreme varus, valgus, and rotational movements around the knee.⁷¹ The cruciate ligaments are intracapsular structures, which can produce a joint effusion when injured. This anatomic relationship is contrasted with the medial and lateral collateral ligaments, which are extracapsular structures. When the medial collateral ligament (MCL) is sprained, there is generally less swelling and no intraarticular effusion because the resultant bleeding from the injured tissues can evacuate the area and the fluid is not restrained within the joint capsule.

Etiology

It is well published that female athletes tear their ACLs at a higher rate than their male counterparts.¹ The common mechanism for both contact and noncontact injuries results in a combined force of external rotation of the hip, valgus stress at the knee joint, and internal tibial rotation with or without knee hyperextension while the affected foot is planted (Fig. 18-1).^{24,73,74,77,91,97}

Clinical Evaluation

The PTA must be aware of various clinical ligament stability tests to accurately and effectively communicate changes in a patient’s stability to the supervising physical therapist (PT) and physician. Although ligament stability tests are part of the initial evaluation procedures used by the physician and PT, the PTA can better understand the static and dynamic restraints of the knee and develop a more comprehensive view of rehabilitation when exposed to the rudimentary concepts of ligament stability testing.

Perhaps the most common, specific, and clinically useful ligament stability test for the ACL is the Lachman examination (Fig. 18-2).⁴⁷ The patient is supine on an examining table with the affected knee flexed to approximately 25° to 30°. One hand is used to stabilize the distal femur, and the other hand grasps the proximal tibia. An anterior and posterior force is gently directed to the proximal tibia. The integrity of the ACL should be observed, and the degree of anterior tibial translation should be noted.

The anterior drawer test (Fig. 18-3) is another clinical examination used to approximate the degree of anterior tibial translation relative to the fixed femur. This examination is a less sensitive test to challenge the integrity of the ACL, and is instead thought to assess the meniscotibial ligaments and the mobility of the menisci on the tibia.⁴⁷ The examination is performed with the patient supine and the affected knee flexed to approximately 90°. Stabilize the affected limb by sitting on the patient’s foot. Both hands should be used to grasp the proximal posterior tibia, with the thumbs on the anterior joint line of the knee. An anterior and posterior force should be exerted to the proximal tibia, and the amount of joint separation of the tibia relative to the femur should be observed.

Other relevant tests for the stability of the ACL incorporate multidirectional rotation examinations to acknowledge the presence of anterolateral rotator instability (ALRI), anteromedial rotatory instability (AMRI), posteromedial rotatory instability (PMRI), and posterolateral rotatory instability (PLRI). ALRI is the more common multiplanar instability encountered.47,91 The Hughston jerk test and pivot shift test are commonly used examinations to sublux and reduce the tibia relative to the femur.⁴⁷

Throughout the performance of the examination, complete muscle relaxation of the hamstrings, quadriceps, and gastrocnemius–soleus muscle group must be maintained. Swelling, intraarticular effusion, and muscle spasm falsely stabilize the knee, rendering the examination meaningless.⁵¹

Operative Management

The PTA must recognize the various surgical procedures used to correct functional instabilities related to ACL injuries and be aware of the short- and long-term ramifications of ligament healing to more effectively deliver sound rehabilitation. Therefore this section provides a rudimentary description of the most common ACL surgical procedures as they relate to the scope and practice of the PTA.

An autograft reconstruction uses tissue from the body of the patient. Various tissues are used for grafts, including the gracilis tendon, fascia lata, semitendinosus tendon, and quadriceps muscle tendon. The bone–patellar tendon–bone (BPTB) autograft is a commonly used graft because of its boney anchor points. The BPTB and bundled gracilis and semitendinosus autografts have all been shown to have greater tensile strength to sheer forces than the original ACL.20,72 An allograft refers to biologic tissue taken from a human cadaver. The major risks of using allograft involve disease transmission and problems with effective sterilization procedures that do not weaken the graft.²⁸

The arthroscopic central one-third BPTB autograft procedure involves harvesting the graft from the involved knee (Fig. 18-4, A) and surgically routing this structure through tunnels placed in the femur and tibia in a way that duplicates normal ACL anatomy, then securing the graft to the bone to allow for stable healing (Fig. 18-4, B-C). A small incision is made in the knee, and a small diameter drainage tube is inserted to help evacuate the joint of residual bleeding, which may increase the risk of arthrofibrosis if allowed to accumulate. This small drain is usually removed after a few days when the bleeding is controlled. Even with the placement of the drain, postoperative arthrofibrosis is a clinically significant problem that can occur.⁴⁵ Sterile bandages are placed over the incisions, and the patient’s leg is often placed in a hinged brace locked in 0° of flexion.

Healing of the graft after surgery

Ligament healing processes and revascularization of graft material are vital concerns in the prescribed rehabilitation program designed by the supervising PT. The appropriate progression of the rehabilitation program depends on the PTA’s awareness of the various stages of healing after an autograft procedure. Once the graft is harvested and surgically routed within the knee, it begins a gradual process of avascular necrosis over the first 6 to 8 weeks.²⁸ The graft gradually loses strength and is quite fragile during the first 2 months after surgery, so excessive loads and forces that would compromise the healing of the graft must be avoided during this time period. The graft slowly revascularizes, and at approximately 3 months the tensile strength of the graft is less than 50% of its original strength.^28,75 Graft strength may take as long as a year to mature and may never reach preoperative tensile strength after the graft cell death and subsequent revascularization process.

Postoperative rehabilitation

The rehabilitation program after ACL reconstruction is designed to protect the graft; reduce pain and swelling; increase joint motion while improving strength, endurance (local muscular endurance, as well as aerobic fitness), flexibility, and proprioception; and ultimately return the knee to full function. This task is organized sequentially and is constantly modified, based on the patient’s individual response to surgery and rehabilitation. The PT and PTA must work together to assess and adjust programs based on the individual’s ability and goals.

In general terms, ACL reconstruction rehabilitation can be organized into three broad, interconnecting phases⁹¹:

1. Maximum-protection phase: From the first day postoperatively to approximately the sixth week after surgery.

2. Moderate-protection phase: From approximately the 7th to the 12th weeks after surgery.

3. Minimum-protection phase: From the 13th week after surgery until return to activity.

This section reviews each phase separately and introduces the PTA to the many variables and individual differences among patients. The importance of reassessment of initial evaluation data and the need for open communication and teamwork with the supervising PT cannot be emphasized too strongly.

Maximum-protection phase (0-8 weeks)

As the graft slowly loses its strength (6 to 8 weeks after surgery), excessive loads and forces that stress the ACL must be avoided. These forces are controlled primarily by joint protection with range-limiting hinged braces and avoidance of anterior tibial translation, shearing forces, and rotational motions.

Control of swelling is important throughout each phase of rehabilitation. Postoperative swelling can have a profound negative effect on the progress of the patient, even with suction drains inserted at the time of surgery. Swelling inhibits muscle contractions, contributes significantly to pain, limits joint motion, and can stimulate arthrofibrosis.⁸⁵ Cryotherapy, elevation of the limb, and the use of a compression wrap help to minimize swelling.

The patient’s ability to achieve early active range of motion (AROM) is an essential component of the maximum-protection phase. Patellar motion (caudal, cephalic, medial, and lateral glide) must be an immediate goal for the restoration of knee motion. Scarring from the graft harvest site and the suprapatellar pouch typically inhibits free patellar motion and full knee ROM.⁸⁵ Initially the PTA must provide gentle stretching of the patella (Fig. 18-5, A–C) and instruct the patient to perform these stretches two to three times daily. Generally, full knee extension is achieved soon after surgery; if not, passive prone or supine knee extension stretches can be used judiciously to gradually increase knee extension (Fig. 18-5, D). In addition to active and passive knee flexion and extension, some authors advocate the use of a continuous passive motion (CPM) device for a limited time very early in this phase.^28,76,91 The use of a CPM device has been suggested to help maintain a normal articular surface as well as to help evacuate synovial joint hemarthrosis and aid in the prevention of joint contracture.^28,76,91 The use of CPM generally is limited to the period immediately after hospitalization.²⁸

Weight-bearing status remains a controversial subject in the literature. In general, weight bearing with crutches is allowed as tolerated immediately after surgery, and patients should be full weight bearing somewhere between 2 and 6 weeks from surgery.21,28,91

The primary focus of strengthening the postoperative ACL patient during the maximum-protection phase is to encourage quadriceps control and hamstring strength. Strengthening exercises during the maximum-protection phase focus on isometric co-contractions of the quadriceps and hamstrings. Hamstring strengthening is emphasized during this phase of maximum protection because they act as dynamic stabilizers to limit anterior tibial shearing forces.28,63,76,77,91 Both standing leg curls and supine leg curls can be initiated during this phase if a brace is used.

Exercises that do not strain the ACL include¹⁰:

 Isometric hamstring muscle contraction exercises at 15°, 30°, 60°, and 90°

 Isometric quadriceps contractions at 0° and 90°

 Simultaneous contraction of the quadriceps and hamstring muscles at 60° and 90°

 Active flexion-extension motion of the knee from 60° to full flexion⁸¹

 Passive flexion-extension motion of the knee without muscle contraction

Open kinetic chain (OKC) active knee extension, with or without resistance, causes an anterior tibial translation force relative to the femur that stresses the new graft. The largest anterior tibial translational forces occur between the knee flexion angles of 30° to 50°.⁸¹ This stated knee range of motion (ROM) should be completely avoided when performing OKC knee extension exercise in the early rehabilitation phases of ACL reconstruction.

Four-way hip (flexion, extension, abduction, and adduction) and calf-strengthening exercises as well as stationary bicycling are also encouraged during this phase. The criteria to be achieved by the patient before advancing to the moderate-protection phase include the following:

 ROM from 0° extension to 120° of flexion

 Full weight bearing (FWB) with normal gait mechanics

 Quadriceps control

 Hamstring control

 Controlled pain and swelling

 A minimum of 6 weeks from the day of surgery

Moderate-protection phase (6-12 weeks)

To advance to this level the patient must be FWB and should be able to demonstrate proper gait mechanics. Immobilization is generally discontinued around the fifth or sixth week postoperatively.²¹ Control of pain and swelling with the use of cryotherapy, compression, and elevation continues as indicated.

Closed kinetic chain (CKC) exercises are a system of interdependent articulated links in which motion at one joint produces motion at all other joints in the system in a predictable manner. CKC exercises and progressive proprioceptive tasks (to stimulate the afferent neural input system) are initiated and progressed throughout this phase. Gradual CKC progressive loads are essential to encourage functional muscle control, confidence in the use of the affected limb, and help stimulate neuromuscular coordination. Initial instruction in CKC exercises begins with the patient braced to protect the healing graft. Standing and shifting of body weight from the nonaffected limb to the affected limb is a safe and appropriate introduction to CKC exercises. Once the patient demonstrates confidence, muscle control, and stability, the brace is removed (with prior consultation and concurrence from the supervising PT) and the patient is allowed to shift weight without braced support. The leg press is used as a CKC exercise in a short-arc motion early in the moderate-protection phase while the patient is braced (Fig. 18-6). Progressive ROM exercises are allowed as tolerated. Standing wall slides also are introduced during the moderate-protection phase if the affected limb is braced and the tibia is kept vertical to avoid an anterior tibial translation force (Fig. 18-7). The short-arc step-up is an excellent exercise used to stimulate quadriceps control and strength. A biofeedback system can be used in conjunction with step-ups to encourage appropriate quadriceps firing patterns (Fig. 18-8).

Stationary cycling should be progressed with added time and resistance throughout this phase. The stationary bicycle is used initially to encourage ROM, but during the middle and later stages of this phase the bicycle can be used as an aerobic conditioning tool if the patient has achieved the required ROM, strength, and stability to perform endurance activities. Stair-steppers and inclined walking can also be introduced during this phase if the ROM and intensity of the resistance on the apparatus are modified and controlled initially to allow for protected joint motion (Fig. 18-9). To stimulate greater strength and local muscular endurance of the quadriceps, the patient can be instructed to perform the stair-stepper in a reverse manner.

Throughout this phase the patient is encouraged to maintain patellar, hamstring, and quadriceps-stretching exercises; normal gait mechanics; a general fitness program of strength and endurance activities that do not stress the affected limb; ice application after exercises; and joint-protection principles.

Criteria that must be met by the patient before progressing to the next phase include the following:

 Full ROM (flexion, extension, and patellar mobility)

 Normalized FWB gait and removal of brace as indicated

 Improved quadriceps strength

 Improved hamstring strength

 Continued control of pain and swelling

 A minimum of 12 to 13 weeks from the day of surgery

Minimum-protection phase (12-24 weeks)

The minimum-protection phase signals the return to more normalized activities and the introduction of more challenging functional activities. Isolated knee ligament stability tests (e.g., Lachman test, anterior drawer test, and pivot shift test) are performed at the discretion of the PT and physician, usually during the moderate-protection and minimum-protection phases of rehabilitation. Ongoing documentation of the stability of the affected limb is essential to justify progression to more challenging exercises and quantify the clinical results of the surgery. The use of isokinetic testing of the involved limb is also left to the judgment of the PT and physician. Generally, isokinetic examinations are reserved for the moderate-protection and minimum-protection phases. Certain precautions must be taken to minimize the tibial translation forces produced with isokinetic testing and training to protect the healing graft. Positioning the pad proximally on the tibia helps to protect the reconstructed ACL against excessive anterior tibial translation forces.⁹¹

More progressive proprioceptive exercises can be initiated when clinical testing demonstrates improved strength, neuromuscular control, and stability of the ligament. The use of a balance board and minitrampoline further challenges the mechanoreceptor system (Fig. 18-10). Standing knee extension with resistance provided by elastic tubing is an excellent CKC exercise that encourages quadriceps control in more functional positions (Fig. 18-11).

A pool running program progressing to a straight-line interval land running program can start later in this phase. Plyometric exercise is also suggested for individuals returning to athletic activities. The inclusion of bilateral ballistic movements, progressing to unilateral movement should be included in the rehabilitation of athletes in order to prepare these individuals for the demands of their sport. It is important to understand that strengthening and plyometric exercises in this phase should not only be progressed from bilateral to unilateral, but also progressed from sagittal, to frontal, to transverse planes of movement.

Progressive strengthening of the entire lower extremity includes isokinetic velocity spectrum training, and isotonic eccentric quadriceps strengthening. The PTA must be constantly aware that rehabilitation after ACL reconstruction involves the entire body and not just the affected limb. Care must be taken to involve all muscle groups, as well as the sensory input systems and aerobic system throughout each phase of rehabilitation. Returning the patient to functional activities is the primary focus of the rehabilitation team.

Frequently, other structures are injured along with the ACL. The rehabilitation plan outlined does not account for possible injury to the meniscus, posterior cruciate ligament (PCL), MCL, lateral collateral ligament (LCL), or joint capsule; associated fractures; or impaired neurovascular structures. The complex nature and vast array of combined injuries dictates modifications at each level of rehabilitation and prolongs the healing process. Common injuries associated with an ACL rupture include a concomitant MCL sprain with a lateral meniscus tear.6,84 In regard to an injured MCL, or débrided meniscus, there will not be a large alteration to the rehabilitation process. In the case of a meniscus repair, it is common for the ACL reconstruction and the meniscal repair to be staged at different times ranging from 3 to 5 months apart. This is done to individually maximize the rehabilitation outcomes of the two surgeries. It has been found that surgical repair of both the ACL and meniscus at the same time yields poorer outcomes than staging the surgeries at separate healing intervals.¹⁴

Posterior Cruciate Ligament Injuries

The primary function of the PCL complex is to restrict posterior tibial translation. It acts as a secondary restraint to tibial varus, valgus, and external rotations.¹⁰⁰ Isolated PCL injuries occur less often than ACL injuries.^7,17,22 PCL injuries are most commonly the result of some sort of trauma to the knee. Although high-velocity knee injuries often result in PCL tears in combination with other ligamentous injuries, this chapter will deal only with isolated PCL injuries.¹⁰⁰

Etiology

The most common mechanism of PCL injury is a fall on a hyperflexed knee that results in a posterior translation of the tibia on the femur (Fig. 18-12).^22,47,100 Other mechanisms include a dashboard injury from a motor vehicle accident that also causes the tibia to translate posteriorly on the femur. Hyperextension injuries can also tear the PCL, however this commonly will result in a concomitant ACL injury.¹⁰⁰

Clinical Evaluation

Clinical examination of the PCL may be very complex and begins with a careful history to determine the mechanism of injury. When eliciting a history from a patient with an acute, isolated PCL tear, unlike with an ACL tear, the patient will often not report feeling a pop or tear.¹⁰⁰ Patients with acute PCL tears will typically have mild to moderate knee effusion, a slight limp, pain in the back of the knee, and will often lack full flexion of the knee. More instability is experienced with combined injuries than with isolated tears. Patients with chronic PCL tears may complain more of disability, having difficulty doing things such as walking up or down inclines secondary to increased tibial movement on the femur.¹⁰⁰

The most accurate test for the integrity of the PCL is the posterior drawer test.¹⁰⁰ This test is performed with the patient supine, the knee at 90° flexion, and the tibia in neutral, external, and internal rotations. As seen in Figure 18-13, A, a positive posterior drawer test is observed when the tibia sags, or subluxes, posteriorly relative to the femur. In cases of isolated PCL tears, there is less posterior tibial translation with internal tibial rotation because the MCL and posterior oblique ligament contribute to this as a secondary restraint. Therefore there will be greater posterior tibial translation with the tibia in external rotation when the MCL and posterior oblique ligaments are not compromised. The examiner may produce a false-positive anterior drawer sign, where the posterior tibial sag actually is being reoriented to the neutral position rather than a true anterior translation occurring (Fig. 18-13, B).

Another PCL laxity test is the Godfrey posterior tibial sag test. The patient is supine with the hip and knee of the affected limb held at 90°. Hold the heel of the affected limb and allow the tibia to translate, sublux, or sag posteriorly by gravity (Fig. 18-14).

Injuries to the MCL are the most common ligament injuries seen in the knee.31,58,98 The MCL can be injured by direct contact to the lateral knee resulting in a valgus stress to the knee (Fig. 18-15, A). Uncommonly, a noncontact valgus or rotational stress to the knee can produce an isolated tear of the MCL when the lower leg is fixed and the tibia rotated externally (Fig. 18-15, B). Upon injury, patients may feel or hear a pop, but more commonly state they felt a tearing or pulling on the medial aspect of the knee. Patients will often present with swelling, and more severe sprains may present with ecchymosis. Patients will also walk with a limp; as they will be very hesitant to fully extend the knee because of increased stress and pain.

Literature shows the higher the grade of MCL lesion, the higher the incidence of an associated ligament injury; with grade III MCL injuries commonly associated with an ACL lesion.³⁰ Because of a high rate of associated injuries to an MCL sprain, one must also bear in mind the anatomical relationship between the MCL and medial meniscus of the knee. The MCL and medial meniscus are attached to one another (Fig. 18-16), which helps in understanding how a blow to the lateral aspect of the knee may also injure the medial meniscus. O’Donoghue⁷³ is credited with describing the unhappy triad as a combined injury to the MCL, ACL, and medial meniscus. However, as time has passed the more clinically common triad includes the MCL, ACL, and lateral meniscus.^6,25,67,84

Etiology

The meniscus can be injured by sudden trauma or gradual degeneration.3,15,32,44 As mentioned, traumatic meniscus injuries are most common in a younger population, whereas degenerative tears occur more frequently to individuals older than 40 years of age.^3,37 Noncontact, weight-bearing injuries to the meniscus usually involve combined forces of knee flexion, rotation, compression, and shear (Fig. 18-19).^3,15,32 Degenerative tears can be subtle and do not usually involve a history of sudden overt trauma. Generally with degenerative tears, some type of insignificant activity (squatting or getting out of a car) precedes the symptoms of pain, swelling, and locking of the knee.

Clinical Examination

A history of some type of twisting injury followed by symptoms of pain, swelling, locking, or catching may indicate meniscal injury. While assisting the PT during the initial clinical examination, the PTA observes various manually applied stress tests to identify if a meniscal lesion is present.

Apley compression and distraction test is used to determine if the injury is ligamentous or meniscal.⁸³ To perform this test, the patient is prone with the affected knee flexed to 90°. The distal femur is stabilized with a strap or hand. The free hand is used to grasp the distal tibia and provide a distraction and internal-external rotation force to the tibia. Pain signifies the possibility of a ligament tear. The compression component of this examination is performed in the same manner, except that the free hand applies a compression and rotational force to the distal tibia. Pain with compression and combined internal and external rotation on the flexed knee suggests the presence of a meniscal lesion.

The McMurray test also is used to reproduce symptoms of a torn meniscus.32,83 The patient is supine with the hip and knee of the affected limb fully flexed. To test for the presence of a medial meniscus lesion, a valgus force to the knee is applied with one hand while an external rotation force is applied and the knee is extended by holding the distal tibia with the other hand. To test for a lateral meniscus tear, a varus force with internal tibial rotation is provided. With either internal or external rotation of the knee, if a tear is present, the patient may experience pain and an audible or palpable snap or pop may occur.

The bounce home test is designed to determine if a torn meniscus is preventing knee extension.⁸³ The patient is supine with the affected knee flexed and supported by the examiner’s hand. The knee is passively extended to full extension. If the meniscus is torn, the knee may not fully extend because the torn tissue blocks extension and creates a rubbery, springy end-feel.⁶¹

The Thessaly test has been shown to be the most accurate clinical test to detect a meniscus tear.⁵² The patient stands on the affected limb with the knee flexed 5° or 20°. The examiner supports the patient’s outstretched arms while the patient rotates their knee internally and externally three times. Joint line discomfort or a sense of catching or locking of the knee is considered a positive test.⁵²

Management

The rationale for treatment options is directly related to the location of the tear in the meniscus and the ability of the meniscus to repair itself. The vascular anatomy of the medial and lateral meniscus is reserved for the peripheral 10% to 30% of its width (Fig. 18-20, A).³ The remaining portions are relatively avascular and aneural. Researchers and surgeons recognize a zone classification of injury related to the vascular supply of the meniscus.^3,40,44,83 The injured meniscus may or may not heal or repair itself, depending on the location of the tear. A zone I tear is recognized as red-on-red because the location of the tear is vascular on both sides (Fig. 18-20, B). Injuries in this area may heal better than those in other areas because of the blood supply. Because of this blood supply in the red-on-red area, some surgeons elect a nonsurgical course of treatment. A zone II tear is located in the red-on-white area of the meniscus (Fig. 18-20, C). A tear in this area has a vascular supply on only one side. These tears also may heal because of the communication with a blood supply. A zone III tear is located in the nonvascular central body of the meniscus called the white-on-white area (Fig. 18-20, D). An injury in this area does not heal because there is no blood supply to support the healing process.

Surgical indications for arthroscopic treatment of meniscal pathology include the following: (1) symptoms of meniscus injury that affect activities of daily living, work, or sports; (2) positive finding from clinical examination; (3) failure to respond to nonsurgical treatment; and (4) absence of other causes of knee pain identified in clinical examination or imaging studies.⁶⁶ The age of the patient, the stability of the knee, the location of the tear, and the integrity of the meniscus should all be considered when deciding on the course of treatment.³²

Surgical options include total meniscectomy (removal of the entire meniscus), subtotal or partial meniscectomy (removal of only the torn portion of the cartilage), meniscal repair (suturing the torn meniscus together), or meniscal transplant.

Operative Management

The microfracture procedure involves several holes being punctured into the subchondral bone, which creates a bleeding response of marrow into the area of the chondral lesion.⁸⁷ The marrow formulates into a fibrocartilaginous clot to protect the underlying subchondral bone.^55,80,87 Osteochondral grafting is a procedure in which cylindrical osteochondral grafts are harvested from the NWB surface of the femoral condyles and strategically placed within the area of the chondral lesion.⁴¹ ACI involves two surgical procedures. The first procedure is an arthroscopic evaluation of the chondral lesion as well as a chondrocyte biopsy from the articular cartilage from a small section of a femoral condyle. Those chondrocytes are then cultured for a approximately 3 weeks and then injected back into the area of the chondral lesion (see Fig. 10-6). The injected chondrocytes are held in place by either a periosteal patch from the patient’s tibia or a synthetic collagen patch.^19,33,62 Variables such as patient age, weight, activity level, chondral lesion size, and other concomitant knee pathology dictate which procedure is best for each patient.

Etiology

Pathology of the patellofemoral joint is one of the most common disabilities of the knee joint in orthopedic and sports medicine.⁹⁴ Several authors have speculated differences in flexibility, strength, and neuromuscular control to be causes of patellofemoral pain (PFP). What seems to be consistent is that people with PFP have decreased gastrocnemius and soleus flexibility⁷⁸ and decreased hip external rotation and abduction strength^78,89; they also tend to demonstrate increased hip internal rotation with CKC activities such as running.⁸⁹ Most patients with PFP will complain of anterior knee pain with prolonged sitting (theater sign), stair ambulation, and squatting motions.

Physical Examination

The physical examination of a patient with PFP should include examining the posture of the patella relative to the femur, the lower extremity muscle stiffness and strength, and the overall lower extremity static and dynamic alignment and how these may cause the patella to track poorly in the trochlear groove of the femur.

In general, the patella is referenced to the femur in three positions (Fig. 18-21). A patellar posture that is more superior than normal is referred to as patella alta^50,67,96 and is associated with greater patellar instability.⁶⁷ Excessive hamstring tightness can increase patellofemoral compression because patellar excursion through knee extension is resisted by hamstrings, requiring more quadriceps force and causing increased compression forces of the patella into the femur (Fig. 18-22).⁵⁰ Testing for rectus femoris and iliotibial band (ITB) inflexibility should also be performed, because these structures have been linked to decreased PFP if flexibility is restored to normal.⁹⁴

In addition to patellar posture and muscle stiffness, the quadriceps angle (Q angle) is a clinical assessment that relates to patellar tracking deviations and variations in the line or angle of pull of the quadriceps on the patella.⁶⁷ The Q angle refers to a line drawn from the anterior superior iliac spine (ASIS) through the center or axis of the patella and distally to the insertion of the patellar tendon on the tibial tubercle (Fig. 18-23, A). The Q angle can be increased by proximal tibial external rotation or distal tibia varus.^50,96 Figure 18-23, B, shows the various angles of muscular pull on the patella and how an increased Q angle can affect the tracking mechanisms of the patella during flexion and extension. Miserable malalignment syndrome (Fig. 18-24) is assessed with the patient in the standing position and provides objective data for the physician and PT about the entire lower extremity kinetic chain, patellar tracking dysfunction, and pain.^50,67,96 This syndrome is characterized by femoral anteversion (internal femoral rotation), “squinting” patellae (patellae facing toward each other), proximal external tibial torsion (which results in what is called the bayonet sign), and foot pronation.^9,96 Miserable malalignment syndrome results in an increased Q angle and can result in lateral tracking of the patella. It has been suggested that the Q angle is not just a valuable tool as a static measurement; it should also be observed during CKC activity, such as a single leg squat.⁷⁹

In light of this information concerning patellar posture, muscle inflexibility and weakness, Q angle, and lower extremity malalignment, the PTA must recognize that the result of these abnormalities is pain and dysfunction related to femoral and retropatellar articular (hyaline) cartilage degeneration from excessive loading of the patellofemoral joint.

Nonoperative Rehabilitation of Anterior Knee Pain

The initial course of treatment focuses primarily on controlling pain and swelling while modifying provocative activity. Activities that cause pain such as running and cycling must be temporarily reduced in order to decrease inflammation. Additionally, ice and nonsteroidal antiinflammatory drugs (NSAIDs) are important modalities in the acute phase to reduce inflammation.

Strengthening of the quadriceps muscle group is initiated by introducing isometric sets that do not produce pain. In some instances, submaximal isometric quadriceps sets are necessary at the beginning of the program to accommodate pain. The vastus medialis oblique (VMO) is the focus of attention when addressing the quadriceps strengthening because of its ability to stabilize the patella superiorly and more importantly, medially.⁹ The superior-medial pull of the vastus medialis muscle directly counteracts lateral tracking syndromes. Equally important, is to perform isolated strengthening exercises of the hip abductors, external rotators, and extensors.

In conjunction with quadriceps and hip strengthening, tight lateral structures that act to pull the patella laterally must be treated manually and with appropriate stretching. Stretching the hamstrings and ITB (Fig. 18-25, A) and performing manual patellar-stretching exercises (Fig. 18-25, B) are essential to counteract anterior knee pain that results for a lateral tracking patella.^94,95 Also, quadriceps, gastrocnemius, and soleus inflexibility should be addressed in the initial phase of rehabilitation.

Once acute inflammation has subsided, CKC strengthening exercises are introduced to promote higher level functional strengthening. Multiplane hip strengthening, leg press, squats, walls squats, and step-ups are all appropriate progressions. ROM, resistance, and step height may all need to be modified to allow the patient to perform without pain. It is important to understand that significant increases of patellofemoral joint stress are shown to happen between 0° and 30° of knee flexion with open-chain exercises, and between 60° and 90° with closed-chain exercises.⁸⁸ Biofeedback units used on the VMO during CKC is an excellent way to emphasize proper muscular activation. CKC exercises should be progressed from bilateral to unilateral as pain and strength allow. Emphasis should be placed on alignment as the exercises progress. Encouraging joint stacking, where the patient controls hip adduction and internal rotation, will reduce valgus angulation across the knee and in turn will help reduce PFP.^64,99

Supportive devices can help dynamically stabilize the patella and promote normal tracking throughout this phase of rehabilitation. Commercially available patellar stabilizing sleeves provide a lateral buttress support to the patella to minimize lateral tracking. Various taping methods can be incorporated for dynamic stability as well. The use of foot orthotics in patients with increased pronation has shown to be useful in decreasing pain by improving lower extremity alignment.¹² These devices may be necessary for the patient to progress through CKC strengthening without pain.

It is important to incorporate pain-free cardiovascular exercise to build muscular endurance and promote patellofemoral joint health. Elevated treadmill walking, both forward and backward, may be most beneficial for muscle activation while minimizing stress to the patellofemoral joint.16,57 Swimming and using a stationary bike and elliptical trainer are all appropriate nonimpact cardiovascular modalities as long as they are pain free for the patient.

When considering return to sport and discharge criteria for patients with PFP it is important for the clinician to thoroughly evaluate lower extremity mechanics as it relates to alignment with running, jumping, and cutting activities. Lower extremity jumping mechanics appear to be consistently different among individuals with PFP.⁹⁹ Conservative treatment programs that include kinematic retraining may improve patient outcomes and prevent recurrence of this common orthopedic condition.^64,79,99

Operative and Postoperative Management for Patellofemoral Pain

Surgical management of patellofemoral disorders can be classified as proximal realignment procedures, distal realignment procedures, and procedures to address articular cartilage abnormalities.⁹⁶

Distal Realignment

The goal behind distal realignment surgeries is to reduce severe patellofemoral compression loads and significant patellar subluxation by surgically removing the extensor mechanism’s insertion (patellar tendon attachment on the tibial tubercle) and reattaching the tibial tubercle to a more mechanically advantageous site to improve the pull of the quadriceps (Fig. 18-26).⁹

Individual circumstances and surgical procedures dictate variations in this initial management plan. Significant modifications in rehabilitation are necessary with distal realignment procedures based on bone and soft-tissue healing and promotion of quadriceps strength. Generally, immobilization with a hinged range-limiting brace is used for 4 to 6 weeks.9,96 Crutches are encouraged for about 6 weeks, with initial NWB progressing to toe-touch weight bearing and then to FWB over the full 6 weeks of immobilization.^9,96 Gradual progression of flexion ROM is advised; achieving approximately 100° of knee flexion for the first 2 weeks and progressing to 120° by 6 weeks.⁹ Isometric quadriceps sets and straight-leg raises are encouraged once pain, swelling and tissue healing allow. With extensor mechanism repair, as well as radical distal realignment procedures, a few weeks’ delay is necessary before initiating quadriceps sets and straight-leg raises so as not to endanger the surgical repair site. Many remedial quadriceps strengthening exercises can be performed in the brace during the early phases of recovery. The moderate protection phase after 6 weeks from surgery will be a similar progression of exercises as those mentioned with nonoperative rehabilitation.

Fractures of the patella can occur with direct or indirect trauma. ⁹⁶ The most common injury involves the patella making contact with a hard surface. Less frequently the patella can be fractured by a violent contraction of the quadriceps. ^65,96 Avascular necrosis (AVN) can result if a transverse fracture occurs, because the vascular supply to the patella is reserved for the central portion of the distal pole, leaving the proximal segment of the transverse fracture prone to AVN.⁶⁵

Operative Management

Surgery for displaced patella fracture is indicated when the bone fragments exceed 3 to 4 mm in separation.⁵⁹ Stabilization of displaced patellar fractures is best accomplished with an open reduction with internal fixation (ORIF) procedure. Figure 18-27 portrays various patellar fracture patterns. The most common fixation devices are tension band wiring and cerclage wiring (Fig. 18-28). The tension band wire is a dynamic compression device that approximates and compresses the patellar fragments. The additional use of cerclage wiring adds to the stability of the repair and allows early joint motion without redisplacing the fracture fragments.⁹⁶

Postoperative management for patella fracture

Generally, the knee is immobilized in 20° of knee flexion to support dynamic compression of the tension band wiring procedure. One week after surgery, active knee extension, submaximal quadriceps sets, and straight leg raises can be initiated. Flexion of the knee out of the immobilizer usually is limited to approximately 100° for at least 6 weeks to allow for proper bone healing. Weight bearing as tolerated (WBAT) with assistive devices is encouraged during the first few weeks after surgery. The patient should be progressed to FWB by the third week. The long progression of quadriceps strengthening exercises and the advancement of full knee flexion correlate with normal bone healing and individual tolerance. Care must be taken not to force aggressive knee extension strengthening exercises with heavy isotonic loads too early in the program. Normalizing gait and progression through CKC step-ups and squats replicates the sequencing outlined in the nonoperative section.

Distal femur fractures generally are classified as extraarticular, unicondylar, or bicondylar65,67 (Fig. 18-29). These fractures are usually managed with an ORIF procedure. Figure 18-30 demonstrates fixation devices used for transverse supracondylar fractures, unicondylar fractures, and type C (T– and Y-pattern) fractures. The method of fixation focuses on fracture site stabilization and fragment apposition while minimizing the pull on the fracture site by the quadriceps, hamstrings, and calf muscles.^59,65

Displaced proximal tibial fractures are treated with an ORIF procedure. Figure 18-31 illustrates the different types of tibial plateau fractures. Various internal fixation devices used with different fracture patterns are illustrated in Figure 18-32. Postoperative management and rehabilitation of tibial plateau fractures follow the course of bone and soft-tissue healing. First, the patient is placed in a leg immobilizer or fracture brace in full extension. Active quadriceps sets are performed and the patient is generally NWB or partial weight bearing, depending on the severity of the fracture. After initial surgical wound healing has occurred, knee flexion exercises can begin based on the patient’s tolerance.

High Tibial Osteotomy

A tibial osteotomy procedure can be performed on patients who demonstrate advanced degenerative joint disease (DJD) of one compartment of the knee.⁶⁷ Most commonly, this is the medial compartment and is characterized by a varus (bow-legged) deformity that creates abnormal loads on the medial aspect of the tibiofemoral joint.⁷² Less frequently, the lateral compartment is involved and creates a valgus deformity (knock-knees) (Fig. 18-33). This procedure is generally considered a temporary solution, approximately 10 years, before a total knee replacement (TKR) is considered.⁶⁷ Patients younger than 50 years of age with greater than 120° flexion have a higher probability of success with a high tibial osteotomy (HTO).⁷⁰

HTO attempts to realign the tibiofemoral joint by surgically creating a wedge in the proximal tibia or distal femur, depending on varus or valgus deformity, and redistributing the forces and compressive loads more evenly across the joint (Fig. 18-34). In valgus deformity associated with lateral tibiofemoral compartment destruction, a distal femur (supracondylar) closing-wedge osteotomy is performed and is stabilized with a plate.^67,86 Depending on the wishes and training of the surgeon, some patients use CPM immediately postoperatively to facilitate early flexion motion.⁸⁶

Postoperative Rehabilitation for High Tibial Osteotomy

Usually the knee is placed in an immobilizer in full extension with a suction drain inserted to help evacuate the excessive accumulation of blood. Initially, strengthening exercises (quadriceps sets, straight-leg raises in the splint, and gluteal sets) are performed and advanced from the first day postoperatively. Manual patellar stretching is encouraged once initial surgical wound healing has occurred, especially with distal femoral wedge osteotomy (preoperative valgus deformity caused by lateral joint compartment disease) because the procedure involves extensive invasion of the quadriceps.⁸⁶ If CPM is not used, the patient is allowed out of the immobilizer several times a day to perform active knee flexion exercises (Fig. 18-35). As patellar mobility (caudal-cephalic motion) improves, progressive knee flexion ROM exercises are added with the patient in a sitting position to allow gravity to influence the flexion range of the affected limb. Care must be taken to manually assist the affected limb from sudden flexion and encourage quadriceps relaxation.

Weight-bearing status after HTO is guided primarily by the time constraints of bone healing.⁸⁶ Usually touch-down weight bearing (TDWB) is allowed after surgery with the aid of crutches or a walker for up to 12 weeks.⁸⁶ Progressive resistive exercises for the quadriceps and hamstrings are initiated gradually within the first 3 to 4 weeks after surgery. Usually ankle weights, Thera-Band resistance, seated isotonic quadriceps and hamstring exercises, and cables and pulleys can be added cautiously during the moderate-protection phase of recovery (7 to 12 weeks).⁹¹ Knee flexion ROM improvement is encouraged by using supine wall slides, seated knee flexion, prone knee flexion, and stationary cycling.

The initiation of functional CKC resistance exercises is deferred until the physician receives radiographic confirmation of secure bone union. Assistive devices for ambulation are discontinued once a minimum of 8 to 12 weeks has passed, fixation of the bone has occurred, and the patient demonstrates good quadriceps strength, improved knee flexion ROM, and confidence in a normalized gait pattern. CKC strengthening exercises can be progressed as discussed with previous sections. One must take caution with progressing CKC exercises as to not inflame an already arthritic knee.

The indications for TKR are primarily to eliminate or reduce pain and improve functional activities in severely disabled patients.34,36,67 Osteoarthritis (DJD) and rheumatoid arthritis contribute significantly to unicompartmental (medial or lateral), bicompartmental (both medial and lateral joint compartments), and tricompartmental (medial, lateral, and patellofemoral compartments) pain and dysfunction.^34,36,67,92

Basic contraindications for TKR are active or recent septic arthritis, a “nonfunctioning extensor mechanism or severe neurologic dysfunction that prevents extension or control of the knee,” and a neuropathic joint.59,67

TKR generally involves removing the degenerated articular surfaces of the tibia, femur, and patella, and replacing these structures with metal, plastic, or a combination of each. The goals are to relieve pain, uniformly transmit forces across the joint, create a horizontal joint in the stance phase of gait, restore anatomic and mechanical axes, provide adequate stability, and improve function.34,36,67,92

Prosthetic implants vary in their design by being constrained, nonconstrained, mobile-bearing, or fixed-bearing. Constrained, or conforming implants, sacrifice the cruciate ligaments (ACL, PCL, or both) and rely on the conformity between the components for stability. Nonconstrained (cruciate-sparing) implants retain the cruciate ligaments.36,67,92 Fixed- bearing prostheses have a polyethylene (plastic) component fixated on the tibial tray. Mobile-bearing prostheses have a polyethylene platform which articulates between the metallic femoral prosthesis and tibial implant. The mobile polyethylene platform allows for better load-sharing throughout the polyethylene and theoretically reduces the wear of this implant.¹³ Studies show similar outcomes with regard to ROM and function with these four implants,^11,46,82 however the prevalence of osteolysis was found to be slightly higher with the mobile-bearing implants.⁴⁶

Prostheses can be secured with or without bone cement. The cementless prosthesis is porous-coated and allows the surrounding bone to grow into and adhere to the prosthesis, creating a direct biologic fixation.³⁶ Cemented implants have been shown to have better survival at 15 years than cementless implants.⁵

Although the most common approach used to perform a TKR is through an anterior medial parapatellar incision, some surgeons are using a minimally invasive approach that spares cutting through the quadriceps. Several authors have shown improved function and a shorter inpatient stay2,27,54 as well as decreased use of narcotics for pain management with the minimally invasive approach.⁵⁴