Hamstrings in cerebral palsy crouch gait.

After observing patients with increased anterior pelvic tilt following medial hamstring lengthening in cerebral palsy crouch gait, we became concerned that the hamstrings may be functionally important hip extensors. To evaluate this, we studied the three-dimensional motion of the hip and knee, calculated hamstring muscle length, and evaluated dynamic electromyography (EMG) of the medial hamstrings in 16 patients with diplegic cerebral palsy and crouch gait to determine if the hamstrings were extending the hip. Twelve of 16 patients exhibited marked prolongation of electrical activity in the medial hamstrings, and in eight of these 12, the hamstrings were contracting concentrically, thus aiding in hip extension during gait. Hamstrings may be important hip extensors in some cerebral palsy patients with crouch gait; however, other deformities contributing to crouch (such as hip flexion contracture) need to be considered before isolated hamstring lengthening is performed in these patients.