Define gait and describe its various phases.
Discuss the various joint angular kinematics and muscle activation requirements in the various phases of gait.
Explain the procedure for static assessment of standing posture.
Discuss various methods for clinical gait assessment.
Describe common gait abnormalities.
Walking becomes almost automatic at an early age and occurs with very little thought or effort. Because walking is a routine part of everyday life, it is often taken for granted until it becomes challenged because of injury or disease. Coincidently and unfortunately, morbidity and mortality rates increase dramatically when one’s mobility becomes compromised.
Abnormal gait patterns arise from traumatic injuries, diseases, or conditions of neurologic or musculoskeletal origin. Deviations in gait may also be associated with aberrant yet subclinical biomechanical abnormalities of the lower extremities. Clinicians should have a working knowledge of normal gait and possess the basic skills necessary to detect abnormal walking patterns. For example, information attained from gait assessment allows the clinician to determine functional abnormalities within joints of the lower extremities. Altogether, information from gait assessment should complement detailed examination of the individual joints of the lower extremities and spine. Therapeutic interventions are implemented according to the findings from such examinations.
This chapter provides an overview of the gait cycle. The purposes of this chapter are to present terminology describing human gait and the basic techniques of gait analysis, discuss normal characteristics of standing static posture, and discuss various pathologies in joints of the lower extremities and how they influence gait. A detailed presentation of gait is beyond the scope of this chapter, and the reader is referred to other sources for more specific information.
Walking, or gait, could be described as “a series of catastrophes narrowly averted,” the act of falling forward and catching oneself, and the process of getting from point A to point B. Gait is a continuous activity that is cyclic and repetitive. As is the case with other continuous activities, individuals are normally able to start or stop their gait with volition. Gait begins from a static standing position (see the section on static standing posture) as the person moves the center of mass forward. This forward excursion of the center of mass must be countered by forward movement of the base of support, or the person would not be able to maintain an upright position and would subsequently fall. The gait cycle occurs from one heel strike to the next heel strike on the same lower extremity ( Fig. 21-1 ).
The feet serve as the base of support and, unlike static postures, must move with the body during gait. During walking, at least one foot is always in contact with the ground (unlike running, which has a flight phase characterized by neither foot being in contact with the ground) ( Fig. 21-2 ). Each forward movement of a foot is a step. A stride consists of two steps, right and left, and represents the gait cycle. The heel is the most commonly used point of reference because the heel is—or should be—the first point of contact with the supporting surface.
A stride can be further dissected into a stance phase, in which a foot is in contact with the ground, and a swing phase, characterized by the foot moving forward. Once the swing foot makes contact with the ground, it enters the stance phase again ( Figs. 21-3 and 21-4 ). Thus, a complete gait cycle for each foot contains stance and swing phases. The phases of gait and the overall gait process contain various observable or measurable gait parameters.
Gait parameters may be recorded from kinematic or kinetic measurements. Kinematic gait evaluation assesses joint range of motion (ROM) and time and distance parameters without consideration of the forces involved. Kinematic assessments may be qualitative or quantitative and require relatively minimal equipment to perform. Kinetic assessments, in contrast, quantify the forces and muscle activity that occur during gait. Although kinetic assessments may be performed in the clinic, most take place in special research laboratories equipped with motion analysis systems, electromyography, force plates, and sophisticated walkways ( Fig. 21-5 ). Even though laboratory gait analysis of kinetic gait parameters offers additional information about an athlete’s gait, the focus of this chapter is on the techniques and terminology associated with clinical kinematic gait assessment. It is recommended that athletes be referred for more sophisticated analysis if the gait abnormalities are too complicated for clinical assessment.
A closer look at the gait phases
The overall gait cycle for the right lower extremity begins with right foot contact, which initiates double support, followed by right single support, double support again, and the right swing phase (a swing phase consists of an initial or acceleration swing phase, midswing phase, and terminal or deceleration phase) ( Fig. 21-6 ). It is important to refer to the side (i.e., right or left) of the lower extremity when referring to the phases of gait. In addition, it is easier to consider only one lower extremity at a time as it undergoes the gait cycle until a level of comfort is achieved with the terminology associated with gait. See Table 21-1 for a comparison of gait terminologies. Caution should be used when interpreting the kinematic data presented because they vary considerably with altered walking speeds.
|Perry/Ranchos Los Amigos||Wall||Hoppenfeld||Whittle|
|Stance||Initial double stance: |
Initial heel contact
|Braking double support||Heel strike||Loading response|
|Single limb support: |
|Single support||Foot flat |
|Terminal double stance |
|Thrusting double support||Push-off||Terminal stance |
|Swing||Initial swing||Swing||Acceleration swing||Initial swing|
|Terminal swing||Deceleration swing||Terminal swing|
Recall that stance phase implies that a foot is in contact with the ground, which normally accounts for approximately 60% of the gait cycle. A closer look at the stance phase reveals a portion of stance in which both feet are in contact with the ground, called the double-support phase, and a portion in which only one foot is in contact with the ground, called the single-support phase ( Fig. 21-7 ). The double-support phase may be further divided into initial double-support and terminal double-support phases ( Figs. 21-8 and 21-9 ). This terminology qualifies portions of double support by describing the functional activity in the lower extremities: (1) on heel contact with the ground in which the lower extremity comes to a stop (initial double support) and (2) when the heel leaves the surface as the foot thrusts against the ground to prepare the lower extremity for the forward propulsion of swing phase (terminal double support). Each lower extremity counters the opposite lower extremity during these phases of double support. Consider the following example: when the right heel makes contact with the ground, the foot is stopping, or braking, whereas the left foot is accelerating, or thrusting, to prepare for the swing phase. Thus, during these periods of double support, each lower extremity acts the opposite of its counterpart.
Angular Kinematics and Muscle Activity: Initial Double Support
Recall that double support inherently implies that both feet are in contact with the ground. One limb is decelerating (initial double support) while the other is preparing to accelerate (terminal double support). In the following descriptions, the reference limb is in the initial double-support phase. Initial double support technically occurs between ipsilateral heel contact and contralateral toe-off and accounts for approximately the first 10% of the gait cycle (see Fig. 21-8 ).
The ankle, immediately before contact with the ground, is in a neutral position (not particularly in dorsiflexion or plantar flexion). When the heel makes contact with the ground, the ankle dorsiflexors act eccentrically to control the foot as it comes to rest on the ground at approximately 7° of plantar flexion. The knee is in extension on contact and moves to about 20° of flexion under eccentric control of the knee extensors. The hip is flexed to approximately 30° on heel contact and is controlled by the hip extensors, which serve to control forward momentum of the trunk. The pelvis is in neutral during initial double support. Eccentric actions of the ankle dorsiflexors and knee and hip extensors provide the braking characteristics, or controlled antagonistic motions, of this phase.
Angular Kinematics and Muscle Activity: Single Support
From initial double support, the foot that recently made contact with the ground begins to bear the entire weight of the body as the contralateral foot leaves the ground during the early swing phase. The foot remaining in contact with the ground is in the single-support phase (see Fig. 21-7 ).
The ankle moves from the plantar flexion associated with initial double support to approximately 10° of dorsiflexion during the single-support phase. The plantar flexors serve to control momentum of the tibia as it rotates forward on the fixed ankle.
The knee moves from 20° of flexion during the initial double-support phase to full extension in single support. This movement is initiated by concentric activity of the knee extensors, which is facilitated by plantar flexor stabilization of the tibia. The body’s forward momentum produces the final degrees of knee extension during the single-support phase.
In the single-support phase, the hip moves to a neutral position by extending from its flexed position during the initial double-support phase. The hip extensors activate to concentrically produce this movement.
The pelvis moves from neutral during initial double support to a laterally tilted position that is away from the leg that is in late single support. The gluteus medius of the leg in single support eccentrically controls this excursion.
Angular Kinematics and Muscle Activity: Terminal Double Support
The stance leg moves from single support into terminal double support as the contralateral swing leg makes contact with the ground (thus, the contralateral leg is entering the initial double-support phase). Terminal double support prepares the leg for the swing phase and occurs between contralateral heel contact and ipsilateral toe-off (see Fig. 21-9 ).
Ankle motion moves from dorsiflexion to plantar flexion in the transition from the single-support to the terminal double-support phase. Plantar flexion reaches approximately 20° at the end of double support as the leg accelerates into the initial swing phase. Concentric activity of the plantar flexors produces this movement.
The knee moves from extension during single support to approximately 35° of flexion at the end of double support. Concentric plantar flexor activity, change in body position, and gravity contribute to this motion.
Hip motion progresses from neutral to approximately 20° of extension at the onset of the terminal double-support phase, which is produced by the continued activity of the hip extensors. At the end of terminal double support, the hip flexes under the influence of concentric hip flexor activity.
The pelvis is level during single support but tilts downward toward the lower extremity that is in terminal double support. Posterior pelvic rotation approaches approximately 4° during terminal double support.
The advancing lower extremity is not in contact with the ground during the swing phase, which accounts for 40% of the gait cycle. The swing phase consists of three subphases: initial, midswing, and terminal (see Table 21-1 for comparative terminology). The initial swing phase ( Fig. 21-10 ) immediately follows terminal double support as the toe leaves the supporting surface (toe-off). The midswing phase follows the initial phase ( Fig. 21-11 ). During midswing, the lower extremity reaches terminal velocity. However, the lower extremity continues forward until it approaches the end of its excursion of motion and begins to decelerate. The terminal swing phase occurs when the lower extremity slows in preparation for contact with the ground ( Fig. 21-12 ). A discussion of the initial, midswing, and terminal swing subphases follows.
Angular Kinematics and Muscle Activity: Acceleration Swing Phase
During the initial swing phase, also known as the acceleration swing phase, the foot leaves contact with the ground (see Fig. 21-10 ). The toe should be the last portion of the foot that has contact with the ground, which is known as toe-off. Dorsiflexion of the ankle occurs during initial swing as it moves to 10° of plantar flexion from the approximately 20° of plantar flexion obtained in terminal double support. The dorsiflexors work concentrically to produce this motion. The knee is flexed to about 35° during initial swing, which is caused by tibial inertia from rapid hip flexion and concentric knee flexor activity. Hip flexion reaches approximately 20° as a result of concentric hip flexor activity. The pelvis is in posterior rotation but begins to rotate anteriorly as it follows the swing leg in its forward motion.
Angular Kinematics and Muscle Activity: Midswing Phase
During the midswing phase, the lower extremity continues its forward flight (see Fig. 21-11 ). In midswing, limb velocity plateaus with respect to the initial swing phase. The ankle continues to dorsiflex and attains a neutral position from concentric activity of the dorsiflexors. At the beginning of midswing, the knee has reached approximately 60° of flexion, and the knee then begins to extend under the influence of gravity and its forward momentum. Eccentric knee flexor activity serves to control this movement. Hip flexion continues to increase to approximately 30° from concentric activity of the hip flexors. The pelvis is level and in neutral rotation.
Angular Kinematics and Muscle Activity: Terminal Swing Phase
The terminal, or deceleration, swing phase is the final subphase of the lower extremity’s forward flight path (see Fig. 21-12 ). The limb must slow in preparation for contact with the ground. The terminal swing phase ends with heel contact, which begins the double-support stance phase again.
The ankle continues in a neutral position that remains until heel contact. The knee continues to extend and reaches 0° at the end of swing phase, controlled by eccentric knee flexor activity. Hip flexion reaches 30°, but muscle activity shifts from concentric hip flexion to eccentric hip extension, which decelerates the limb in preparation for contact with the ground. The pelvis rotates forward approximately 4° during the terminal swing phase.
The descriptions of the gait cycle portrayed in this section are concise and intended to provide a basic overview. For more information on the gait cycle, the reader is referred to additional sources.
Static Assessment of Standing Posture
Upright standing posture is discussed before gait analysis techniques because upright standing is the posture in which walking occurs. In addition to its potential effect on gait, abnormal posture appears to play a role in predisposition to injury. Deviations from normal posture are considered abnormalities or malalignments. Sometimes postural abnormalities cause deviations in gait, but it is important to note that not all gait deviations are caused by postural abnormalities. Furthermore, not all gait deviations are evident in a static postural assessment. The clinician should perform both static standing posture and dynamic gait assessments for a comprehensive clinical picture of the athlete.
Clinical postural assessment is subjective. Whenever feasible, the athlete should remove as much clothing as possible to allow visualization of anatomic landmarks. It may be helpful to mark various landmarks with a grease pen, a water-based marker, or colored stickers to aid visual assessment (see Box 21-1 for list of common landmarks to assess during evaluation of posture). A plumb line should be used to provide the examiner with a true reference to vertical. Photography and videography increase the reliability of postural assessment. Image-processing applications such as Image J *
* Image J is an open-source image processing and analysis tool written in Java. It runs as 32- or 64-bit modes on Linux, Mac OS X, and Windows ( rsbweb.nih.gov.easyaccess2.lib.cuhk.edu.hk/ij/ ). One can import video files and then analyze individual frames with various analysis tools within the application. The angle-drawing tool is particularly helpful to estimate joint angle kinematics.have been validated for photographic assessment. In addition, a posture grid †
† Some photographic editing applications allow the superimposition of gridlines on photographs. This would serve as a substitute for a physical posture grid and plumb line.placed in the background of the respective view allows quantification of deviations in posture ( Fig. 21-13 ). Static postures should be assessed from the anterior, lateral, oblique, and posterior views. These respective views provide a comprehensive postural assessment.
Both clavicular heads
Anterior superior iliac spines
Middle of the patella
Vertebral spinous processes:
C7 or T1
T3, T6, T9, and T12
L3 and L5
Center of the calcaneus
Lateral femoral condyle
The plumb line in the anterior view is in the sagittal plane. The plumb line should pass from the middle of the cranium and bisect the body into right and left portions as it passes down the midline of the trunk ( Fig. 21-14 ). Plumb line assessment allows the clinician to detect subtle deviations in posture associated with asymmetry.
Beginning proximally, the position of the head, jaw, and nose is assessed. The head and neck should be in a neutral position and straight on the shoulders. Abnormal findings commonly include cervical rotation or lateral flexion to one side. A normal jaw posture implies that the lips are approximated with the teeth slightly apart while the tongue rests on the roof of the mouth posterior to the upper row of teeth. The nose is aligned with the manubrium and xiphoid process of the sternum.
The shoulders should be even in height, although the dominant shoulder may appear somewhat lower in well-developed individuals. Trapezius muscle bulk is equal on both sides but may be somewhat increased on the dominant shoulder.
The lower extremities should also have symmetry in the anterior view. Two particular judgments are ankle position and leg interspace. Ankle position is assessed by observing the medial longitudinal arch and the positions of the talus and navicular. If the person is flat-footed, the talus and navicular may appear relatively low in position, which is known as pes planus. A high arch, or pes cavus, is another abnormality observable from the anterior view. The position of the calcaneus also contributes to ankle posture but is obscured in the anterior view and must be assessed posteriorly (see the posterior view section). The leg interspace is the space between the lower extremities during normal standing. If an athlete has genu valgum (knock-kneed), the interspace is quite small in comparison to someone with genu varum (bowlegged).
The lateral view of static standing posture should be made from both sides of the body. A straight line (plumb line) is placed at the center of the cranium and should run posterior to the ear, pass through the acromion process at the shoulder, split the lateral epicondyle of the humerus at the elbow, bisect the high point of the iliac crest, pass through the lateral femoral condyle at the knee, and complete its course anterior to the lateral malleolus at the ankle ( Fig. 21-15 ).