Surgical treatment of knee dysfunction in cerebral palsy.

The prerequisites for normal gait are: (1) stability in the stance phase of gait, (2) clearance of the foot in the swing phase, (3) proper foot preposition in swing, and (4) an adequate step length. In the stance phase, the knee provides shock absorption and energy conservation; in the swing phase, it allows foot clearance. To accomplish these functions, the knee must extend fully in stance and flex approximately 60 degrees in swing. Consequently, balanced muscle action at the hip, knee, and ankle joints, combined with adequate acceleration from the hip flexor and triceps surae muscles, is essential. In the crouch gait of spastic cerebral palsy, hamstring lengthening alone often converts the flexed-knee gait to an extended-knee, stiff-legged gait with inadequate swing-phase knee flexion. This unwanted conversion is due to cospasticity of the quadriceps and hamstring muscles. Restoration of normal knee function in patients with spastic paralysis is more successful when fractional hamstring lengthening is combined with a transfer of the distal rectus femoris tendon to either the iliotibial band or the distal tendon of the semitendinosus.