Adaptations during the stance phase of gait for simulated flexion contractures at the knee.

Adaptations in the stance phase of gait to knee flexion contractures simulated by a knee-ankle-foot orthosis were studied in 20 healthy women (mean age: 25 +/- 3.6 years). Stride characteristics, joint postures, floor reactions, and indwelling electromyographic activity of the lower gluteus maximus, vastus lateralis, long head of the biceps femoris, and soleus muscles were measured during walking with the orthosis, with and without contracture simulation. Simulated knee flexion contracture resulted in decreased stride length and velocity and increased forefoot weight bearing and flexion posture in stance. Increases were also seen in magnitude and/or duration of flexion floor reaction torques and gluteus maximus, vastus lateralis, and soleus muscle activity. The addition of a restriction of plantar flexion resulted in a further decrease in velocity and stride length and a small increase in hip extension posture. These results show that knee flexion contractures, simulated in healthy subjects, cause a decrease in gait function with a simultaneous increase in muscular demand.