The aim of this study was to examine the effectiveness of Ilizarov method in severe congenital flexion deformity of the knee. This was a retrospective study of eight consecutive bilateral cases (five girls and three boys, with mean age of 4 years, involving 16 knees) with minimum 2-year follow-up. Four patients had multiple congenital contractures and two patients each had popliteal pterygium syndrome and complete tibial hemimelia. All patients were treated with Ilizarov fixator and gradual correction (additional soft tissue releases in three knees). Six patients had bilateral foot and ankle deformity treated with the same fixator, and cases with tibial hemimelia had centralization of fibula and quadriceps reconstruction. Flexion deformity could be corrected in all cases. Mean duration of dynamic phase was 78.5 (55-108) days, that of static phase was 42.4 (7-100) days, and total duration of external fixation was 120.9 (87-186) days. At mean follow-up of 34.5 (23-60) months, flexion deformity improved from the preoperative value of 74.9° (50°-130°) to 13.7° (10°-16°), and passive arc of motion of knee improved from the preoperative value of 38.8° (20°-55°) to 83.6° (55°-110°). Both were statistically significant (P < 0.0001). All patients (previously nonambulatory) were ambulatory with brace and support. All patients faced pin-tract and skin complications that were successfully managed. Ilizarov method is effective in severe congenital flexion deformity of the knee in improving ambulatory status. Realignment of quadriceps mechanism and limb mechanical axis (including ankle and foot deformities) must be given due importance. Minor recurrences of deformity must be expected in all cases.