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 exten
sors. To evaluate this, we studied the three-dimensional motion of the
hip and knee, calculated hamstring muscle length, and evaluated dynam
ic electromyography (EMG) of the medial hamstrings in 16 patients with
diplegic cerebral palsy and crouch gait to determine if the hamstring
s were extending the hip. Twelve of 16 patients exhibited marked prolo
ngation of electrical activity in the medial hamstrings, and in eight
of these 12, the hamstrings were contracting concentrically, thus aidi
ng in hip extension during gait. Hamstrings may be important hip exten
sors in some cerebral palsy patients with crouch gait; however, other
deformities contributing to crouch (such as hip flexion contracture) n
eed to be considered before isolated hamstring lengthening is performe
d in these patients.