The definition of the gait cycle is based on a reference extremity (for example, the right foot) from a defined event such as heel contact until the next occurrence of that event (contact with the heel of that same foot). The gait cycle is often based on 100% and can be further broken down into the stance phase and the swing phase (Fig. 14-1). The stance phase is defined as the portion of the gait cycle where the foot is in contact with the ground whereas the swing phase is the portion where the foot is off the ground. A step is defined as contact on one foot until contact with the other (right to left or left to right). A stride is defined as contact with the one foot until contact with the same foot (right to right or left to left). The stance phase of the gait cycle is typically about 60% of the gait cycle, whereas the swing phase is about 40% (see Fig. 14-1). The reason why the stance and swing phases are not 50% is due to the relatively short period of double support (10%) within the gait cycle. This small portion of support phase is the period where the weight is transferred from one limb to the other.

Fig. 14-1 Terminology to describe the events of the gait cycle. Initial contact corresponds to the beginning of stance when the foot first contacts the ground at 0% of gait cycle. Opposite toe off occurs when the contralateral foot leaves the ground at 10% of gait cycle. Heel rise corresponds to the heel lifting from the ground and occurs at approximately 30% of gait cycle. Opposite initial contact corresponds to the foot contact of the opposite limb, typically at 50% of gait cycle. Toe off occurs when the foot leaves the ground at 60% of gait cycle. Feet adjacent takes place when the foot of the swing leg is next to the foot of the stance leg at 73% of gait cycle. Tibia vertical corresponds to the tibia of the swing leg being oriented in the vertical direction at 87% of gait cycle. The final event is, again, initial contact, which in fact is the start of the next gait cycle. These eight events divide the gait cycle into seven periods. Loading response, between initial contact and opposite toe off, corresponds to the time when the weight is accepted by the lower extremity, initiating contact with the ground. Midstance is from opposite toe off to heel rise (10% to 30% of gait cycle). Terminal stance begins when the heel rises and ends when the contralateral lower extremity touches the ground, from 30% to 50% of gait cycle. Pre swing takes place from foot contact of the contralateral limb to toe off of the ipsilateral foot, which is the time corresponding to the second double-limb support period of the gait cycle (50% to 60% of gait cycle). Initial swing is from toe off to feet adjacent, when the foot of the swing leg is next to the foot of the stance leg (60% to 73% of gait cycle). Mid swing is from feet adjacent to when the tibia of the swing leg is vertical (73% to 87% of gait cycle). Terminal swing is from a vertical position of the tibia to immediately before heel contact (87% to 100% of the gait cycle). The first 10% of the gait cycle corresponds to a task of weight acceptance—when body mass is transferred from one lower extremity to the other. Single-limb support, from 10% to 50% of the gait cycle, serves to support the weight of the body as the opposite limb swings forward. The last 10% of stance phase and the entire swing phase serve to advance the limb forward to a new location. (From Neumann DA: *Kinesiology of the musculoskeletal system: foundations for physical rehabilitation*, ed 2, St Louis, 2010, Mosby.)

The stance phase has been described as having two basic functions: weight acceptance and single limb support; whereas the swing phase has one primary function: limb advancement.¹⁶ Figure 14-1 depicts the phases within the stance and swing phases of the gait cycle. Contact with the floor is often made with the heel (often called heel contact or initial contact). Perry¹⁶ has described the first 15% of the gait cycle portion as when the foot functions as a heel rocker or first rocker. During this part of the gait cycle, impact forces tend to be large at 1 to 1.5 times body weight, depending on the speed of locomotion. Once the foot becomes flat on the ground the tibia advances forward over the stance foot. Perry¹⁶ has described this as the ankle rocker or second rocker. This phase of the gait cycle is also called midstance phase. The terminal stance phase begins when the heel is raised off the ground (about 40% of the stance phase) until the opposite foot makes ground contact. The final phase of stance phase of the gait cycle is the pre-swing phase, which begins with heel strike of the contralateral limb and ends with toe off. When the heel is lifted from the floor (heel off), this can also be described as the toe rocker or third rocker.

The swing phase of the gait cycle has three portions: pre-swing, mid-swing and terminal swing phases. The pre-swing phase begins with double limb support and ends with toe off. This phase is primarily made up by the foot moving off the ground and is critical for limb advancement. This phase takes place as the gait cycle is 60% and 75% complete. Mid-swing phase is from 75% to 85% of the gait cycle, when the swing limb advances in front of the stance limb. The terminal swing phase completes the remainder of the swing phase until heel contact.

CHARACTERISTICS OF NORMAL GAIT

Many factors can influence gait, such as age, pain, strength, range of motion (ROM), walking speed, and fitness level. The extent of the influence of such factors can be quantified by taking simple measurements to characterize and assess a person’s walking performance with a tape measure, goniometer, and stop watch. The measures are stride or step length, step width (walking base), foot progression angle, walking speed, and cadence. Typical stride length reported from the literature has a range of 1.33 to 1.63 m in healthy individuals.4,5,7,9–12,15,18 Males generally have a greater step length than females. Step width or the horizontal distance between feet while walking has a range of 0.61 to 9.0 cm.^11,12,17,20 Foot progression angle or angle of toe out has been reported to range between 5.1° and 6.8°. Various definitions for foot placement can be seen in Figure 14-2. The average typical walking speed is 1.49 m/sec for men and 1.40 m/sec for women, ranging between 3 to 4 miles per hour for both genders.^{2–4,14,18,21} Average walking speed can be measured over a specific distance with a stop watch. Speed can be calculated by taking the distance over the elapsed time taken to walk the prescribed distance. Walking speed is based on cadence (number of steps per minute) and step length. Average cadence has a range of 107 to 125 steps per minute.^{2–4,14,18,21} To increase walking speed, one can increase cadence or step length. Self selected walking speed is typically slower for women than in men. With the slower gait speed there appears to be a shorter step length and faster cadence for women than men. Keep in mind that all measurements of gait are largely dependent on walking speed.

Fig. 14-2 Terms used to describe foot placement on the ground. (From Whittle MW: *Gait analysis: an introduction*, ed 4, St Louis, 2008, Butterworth-Heinemann.)

As walking speed increases, stance time generally decreases in comparison to swing time. Most of the reduction in stance time comes from a reduction in double support time (due to the reduction in stance time on both limbs). Overall, these simple measures of gait can give the clinician an impression of the overall gait pattern. These measures are often called the temporal spatial measures of gait.

Normal gait is not entirely symmetrical.¹⁸ Small asymmetries in gait are often considered typical. With slower walking speeds, greater amounts of asymmetry have been observed in healthy individuals with normal gait. Thus one must be able to identify if these subtleties in normal gait have clinical relevance.

Movement patterns of the joints can provide additional insight to an individual’s gait. Researchers in motion analysis laboratories have provided detailed three-dimensional data on the range of joint motion during walking. Sagittal plane motion patterns are the largest motions and represent the most studied parameters, whereas frontal plane and transverse plane motion patterns are smaller motions that have been less studied. Estimations of these motions can be visually observed by the health professional at a distance from the side for sagittal motions or from the front or behind for frontal plane motions as the patient is walking. Pure transverse plane rotation is difficult to observe in a clinical setting because an aerial perspective is required. One likely has to combine side and front views to estimate transverse plane motion.

Motions of the Foot, Ankle, Knee, Hip, and Pelvis

Foot

There are several joints within the foot, with some motion occurring at each of the joints during gait. However, most of the required motion at the foot is from the first metatarsophalangeal joint. At the instant of heel off during the terminal stance phase of gait, the first metatarsophalangeal joint typically hyperextends 45° to 55° as the ankle actively plantarflexes. The first metatarsophalangeal joint then returns to nearly 0° during the remainder of the gait cycle. A limitation in this passive hyperextension may cause compensations in other joints in the chain.¹⁹

Rearfoot motion is movement based on the motion of the posterior aspect of the heel relative to the posterior aspect of the lower leg in the frontal plane. This has been used as an estimation of the triplanar motion of pronation that occurs during the stance phase of gait when the foot everts, abducts, and dorsiflexes. When the posterior aspect of the heel is more everted relative to the lower leg the foot is considered to be in a more pronated position. With foot contact, the rearfoot is slightly inverted and immediately begins to evert or pronate until the midstance phase. At the instant of heel off during the beginning of terminal stance phase, the rearfoot is nearly neutral and then begins to invert until toe off. This inversion of the rearfoot is thought to describe the triplanar motion of supination during terminal stance when the foot inverts, adducts and plantarflexes.

Ankle

At ground contact, the ankle is primarily in a neutral position (0°, at a right angle to the tibia, neither plantarflexed nor dorsiflexed). After contact, the ankle plantarflexes about 5° so that the foot becomes flat on the ground.¹⁶ This motion is controlled eccentrically by the ankle dorsiflexor muscles. Next, the tibia rotates over the stance foot resulting in maximum ankle dorsiflexion. This motion is generally controlled eccentrically by the ankle plantarflexor muscles. During the pre-swing phase of gait, the ankle plantarflexes to propel the person forward. An inadequate amount of plantarflexion may be due to a lack of ankle power, resulting in a reduction in step length during gait. During swing, the ankle must dorsiflex to allow for foot clearance as that leg steps forward for ground contact.