This study evaluated the differences in muscle-tendon lengths during single limb support between recurvatum and crouch knee in patients with cerebral palsy. Group I consisted of 14 patients who had recurvatum knee, whereas group II consisted of 17 patients who had crouch knee. Compared with group II, group I had decreased ankle power and plantarflexion moment and only the average muscle-tendon lengths of the gluteus medius and vasti was decreased. There were no differences in other muscle-tendon lengths. Recurvatum and crouch knee could occur with similar muscle-tendon lengths of the gastrocnemius, semimembranosus, biceps femoris, and rectus femoris.