Contractures of the knee joint can interfere with orthotic fitting and prevent the child from being upright and ambulatory. Two types of knee contractures are seen: flexion and extension. A flexion deformity is more common in the thoracolumbar level and, when beyond 20 degrees, will require surgical treatment. The author reviewed his surgical experience with 23 knees undergoing a radical flexor release. With an average follow-up of 38 months, 10 knees showed no contractures, 11 knees 5 to 10 degrees of flexion deformity, and 1 knee a 15 degrees deformity. Three knees had a simple tendon release with poor results. Fifteen knees with an extension contracture were treated surgically (VY quadriceps lengthening). With a follow-up of 43 months, eight knees had 120 degrees of flexion, five 90 degrees, and two only 45 degrees. Three knees showed full recovery of quadriceps strength. It is concluded that a knee flexion deformity will respond well to the radical flexor release. Prolonged splinting is important in order to avoid recurrence. An extension contracture can be successfully treated by the VY quadriceps plasty with improvement in the child's gait and sitting.