Equilibrium involves the maintenance of balance in relation to gravity and to the direction of movement in order to retain a vertical posture. The unstable center of gravity that prevails in walking must shift within narrow limits from side to side and forward as the weight is borne first on one foot, then on the other. This is accomplished through the activity of highly sensitive postural and righting reflexes that have both peripheral (stretch reflexes) and central (vestibulocerebellar reflexes) components. These reflexes are activated within 100 ms of each shift in the support surface and require reliable afferent information from the visual, vestibular, and proprioceptive systems.
Propulsion is provided by leaning forward and slightly to one side and permitting the body to fall a certain distance before being checked by the support of the leg. Here, both forward and alternating lateral movements must occur. In contrast to walking, running requires that both feet are momentarily off the ground, necessitating a forward drive or thrust by the trailing leg.
Because normal body posture and locomotion require intact vestibular function, proprioception, and vision (we see where we are going and adjust our steps), the effects of deficits in these senses are worth noting. A blind person—or a normal one who is blindfolded or walks in the dark—moves cautiously, with arms slightly forward to avoid collisions, and shortens his step slightly on a smooth surface; there is less rocking of the body and the gait is unnaturally stiff and cautious.
Pain in the hips or knees can lead to a disorder (antalgic gait) that can be challenging to distinguish from neurological causes of gait problems. Slowness of the swing phase and reduction in the amount of time spent with the painful limb in contact with the ground may be clues to recognizing rheumatological and orthopedic causes of a gait disorder. Of course, the patient’s description of pain in certain positions or actions makes the problem self-evident and maneuvers, such as passive moving the leg about the hip, further expose the source of gait disruption. At times, musculoskeletal disorders produce little pain but alter the gait pattern as a result of protective and compensatory responses. Weakness of one or a group of adjacent muscles impart a peculiar but identifiable appearance to walking, some aspects of which are detailed further on.
Examination of the Patient With Abnormal Gait
When confronted with a disorder of gait, the examiner should observe the patient’s stance and the positions of the legs, trunk, and arms, and their interrelationships. It is good practice to watch patients as they enter the examining room, when they are apt to walk more naturally than during the performance of commanded tasks. Walking without the support of a cane or the arm of a companion brings out a certain stiffness of the legs and firmness of the muscles.