14
Gait
Thomas W.. Kernozek and John D.. Willson
1. Define and describe basic components of the gait cycle.
2. Discuss the two phases of gait.
3. Identify and describe each component of the two phases of gait.
4. Define and describe common gait deviations.
5. Define and instruct appropriate gait patterns.
6. Outline and describe terms used to define weight-bearing status during gait.
7. Identify and discuss the appropriate use of assistive devices.
GAIT CYCLE TERMINOLOGY AND PHASES OF GAIT
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.
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.
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.
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.
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
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.
Knee
The knee is close to full extension at ground contact. The knee flexes 10° to 15° as the foot becomes flat on the ground during the initial 15% of the gait cycle. Knee flexion facilitates the absorption of forces during impact as the quadriceps muscles function eccentrically. After foot flat, the knee extends until about 40% of the gait cycle. As the ankle plantarflexes during terminal stance phase, the knee flexes to about 35° at toe off. Knee flexion during this phase reduces the overall length of the limb allowing for adequate foot ground clearance. The knee continues to flex to its maximum at about 60° during mid swing. Later in mid and terminal swing, the knee extends to nearly full extension in preparation for ground contact.16 The knee motion reported during gait in the frontal plane is minimal (within 10° of abduction and adduction during the entire gait cycle) and appears to be quite variable.1,3,8 A small amount of medial rotation of the knee that occurs during early stance and appears to be linked with foot pronation has been reported.8 During midstance and throughout the swing phase the knee appears to laterally rotate back to neutral. Rearfoot pronation is accompanied by tibial medial rotation with knee flexion. This is thought to be important for shock absorption occurring with foot impact with the ground. Tibial lateral rotation occurs later in stance with foot supination and is accompanied by knee extension.