ground. Impairment of these same muscle groups can result in a drop foot pattern (also called a high steppage gait) seen during swing phase. Because the muscles do not dorsifl ex the ankle at swing phase, the foot is in a dropped position and may not clear the ground as the limb attempts to swing forward. To compensate for this inability to clear the foot off the ground, the person may use excessive hip and knee fl exion to lift the entire limb farther from the ground (Fig. 14.9B). People who cannot control dorsifl exion when walking may benefi t from an ankle-foot orthosis either to assist with dorsi- fl exion or to prevent plantar fl exion depending on their specifi c needs.
GLUTEUS MAXIMUS LURCH
If the gluteus maximus is weak and cannot maintain the hip in extension, it jackknifes into fl exion when the heel strikes the ground. The hip then moves into hyperex- tension at mid-stance. This extreme rocking forward and backward motion of the trunk and hips is called a gluteus maximus lurch (Fig. 14.10A). Weakness in the
knee extensors can produce genu recurvatum, a condition in which the knee remains in full extension or hyperex- tension throughout the stance phase. The weak quadri- ceps have diffi culty controlling knee fl exion as the limb is loaded, resulting in decreased knee stability at mid- stance. The trunk leans anteriorly to move the COM anterior to the axis of the knee. This produces passive knee extension in an attempt to increase knee stability without the function of the knee extensor musculature (Fig. 14.10B).
TRENDELENBURG GAIT
Hip abductor weakness of the stance limb can produce excessive downward dropping of the pelvis on the non– weight-bearing side. This pelvic drop is called a posi- tive Trendelenburg sign. To compensate for this hip abductor weakness when walking, the trunk leans later- ally toward the stance limb in a compensatory Trendelen- burg gait (Fig. 14.11). If the weakness is bilateral, and the trunk leans to each side during stance phase, the result is known as a waddling gait.
A
B Figure 14.10 Weak hip and knee extensor muscles can result in gluteus maximus lurch (A) or genu recurvatum (B).
