habitual patellar dislocation is a rare condition where the patella dislocates during flexion and relocates during extension unlike chronic patellar dislocation that occurs during both flexion and extension of the knee , and it usually presents without pain or swelling . a variety of surgical techniques have been introduced for the treatment of habitual dislocation of the patella with genu valgum . among them , osteotomy combined with proximal soft tissue realignment procedures including lateral release and medial reefing has been commonly performed . it has been known that significant treatment results can be obtained with combined procedures , not with a single procedure . we here report a case of habitual dislocation of the patella with genu valgum treated with a corrective osteotomy of the distal femur combined with lateral release and medial reefing . a 23-year - old man visited our institution due to lateral dislocation of the left knee in flexion and instability that had persisted for 7 years ( fig . 1 ) . the patient had a history of femoral growth plate fracture treated conservatively at 13 years of age . in the physical examination , the apprehension test was positive . in the radiographic examination , the congruence angle , sulcus angle , q - angle , and insall - salvati ratio was 44.17 , 152 , 18 , and 1.15 , respectively . the tibiofemoral angle measured from the weight - bearing radiograph was 16 , indicating genu valgum deformity , and hypoplasia of the lateral femoral condyle of the left knee was observed . arthroscopic examination revealed the hypoplasia of the lateral femoral condyle , outerbridge grade ii cartilage damage on the lateral articular surface , and contracture of the lateral retinaculum and vastus lateralis . a lateral retinacular release and an open - wedge distal fermoral varus osteotomy were followed by additional procedures including lateral release and medial reefing because dislocation was still present after the osteotomy . when lateral dislocation of the patella in flexion was no longer observed , a bone graft was inserted into the osteotomy site . weight bearing was gradually permitted and complete weight bearing was allowed at the 3 postoperative month . on the postoperative radiograph , the congruence angle , sulcus angle , q - angle , and insall - salvati ratio was 15.75 , 152 , 2.3 , and 1.03 , respectively . the tibiofemoral angle was corrected to 4 of valgus on the weight - bearing radiograph . the causes of habitual patellar dislocation include contracture and fibrosis of the quadriceps femoris , vastus lateralis , and lateral retinaculum , abnormal iliotibial band attachment , repeated intramuscular injections into the thigh , patella alta due to the abnormal position of an elongated patellar tendon , systemic ligament laxity , dysplastic lateral femoral condyle , and genu valgum2 - 4 ) . a variety of surgical techniques have been introduced for the treatment of habitual dislocation of the patella . however , it has been known that combined procedures , not one single procedure , should be performed to achieve relatively satisfying treatment results . hnevkovsky et al.4 ) attributed habitual patellar dislocation to contracture of the quadriceps femoris and introduced a technique to lengthen the muscle with the use of a lateral retinacular release and quadricepsplasty , which did not bring about complete flexion in their patients . in our patient , genu valgum and lateral femoral condyle hypoplasia following a growth plate fracture were thought as the cause of the dislocation . a quadricepsplasty was considered unnecessary because he had no contracture of the quadriceps femoris . however , lateral retinacular release alone was not sufficient to achieve joint reduction . they are broadly classified into proximal and distal realignment procedures or bone and soft tissue realignment procedures . proximal soft tissue realignment procedures including lateral release and medial reefing and distal realignment procedures are commonly used in adults . in particular , distal realignment procedures are limited to adult patients with 20 of q - angle because they could result in premature growth plate closure in children with open growth plates . however , vastus medialis advancement can cause an increase in pressure on the knee , which eventually results in patellofemoral arthritis . although the patient 's medial retinaculum was extensively elongated , it was thick enough to be reefed and sutured . therefore , a reconstruction using a medial patellofemoral ligament allograft was not considered necessary and the reduction was maintained at the follow - up examination . appropriate surgical treatment methods for habitual dislocation of the patella with genu valgum still remain controversial . gao et al.6 ) reported that flexion contracture of the quadriceps muscle was the cause of lateral dislocation of the patella in children and the sustained contracture also resulted in genu valgum . a release of quadriceps femoris contracture can be effective in correcting genu valgum in children who have hypoplasia of the lateral femoral condyle due to growth plate damage7 ) . still , the ideal age for the treatment has yet to be established . in adults , if genu valgum deformity remains after realignment due to the unstable patella , symptoms may also persist . coventry8 ) reported that femoral supracondylar varus osteotomy should be performed in patients with 12 of symptomatic genu valgum or with 10 of tilt of the articular surface . healy et al.9 ) recommended to perform corrective osteotomy of the distal femur for 15 of genu valgum . shen et al.10 ) suggested proximal soft tissue realignment and distal femoral osteotomy and anteromedial tibial tubercle transfer to treat genum valgum with 20 of femorotibial angle . therefore , we thought proximal soft tissue realignment alone was not sufficient to realign the patella and performed a femoral supracondylar osteotomy in addition . femoral supracondylar osteotomy for genu valgum can be performed using an open or closed technique , but the latter has been associated with postoperative joint stiffness7 ) . considering that the risk of joint stiffness would be high in our patient because of the complex procedures including lateral retinacular release and medial reefing , we used an open osteotomy technique and took care not to damage the joint capsule during surgery . we believe that clinical improvement of habitual dislocation of the patella can be obtained with correction of soft tissue imbalance and contracture and realignment of the patello femoral and tibiofemoral joints . in particular , soft tissue procedures should be followed by bony procedures including femoral supracondylar osteotomy in cases of habitual dislocation of the patella with genu valgum .
habitual dislocation of patella is a rare disorder . 
 sometimes it is associated with angular deformity such as genu valgum . 
 we experienced habitual patella dislocation associated with genu valgum that was treated with corrective osteotomy of distal femur and soft tissue realignment procedure including lateral release and medial reefing .