A 50-year-old woman presented with iatrogenic habitual dislocation of left patella from childhood and pain from past 3 years. She recalled a childhood surgery over middle third of left thigh (incision and drainage). Few years after the surgery, she started noticing the giving way of patella and lived for 38 years without much disability. She was carrying out her daily activities without much pain or symptoms, but she was never symptom free during this period.\nPhysical examination did not reveal general joint laxity or malalignment of the lower extremity. There was a healed surgical scar over middle and lower third lateral aspect of the left thigh. Although the patella was in the femoral trochlear groove in extension, it dislocated laterally with 25 degrees of knee flexion. She complained slight discomfort by an apprehension test, but was not very painful even when dislocated. The passive lateral patellar tilt test was negative since the soft tissue attachment to the lateral border of the patella was diffusely stiff and tight. Radiological examination revealed evidence of patella alta as defined by Insall and Salvati,[] and Q angle was 18 degrees. Clinically and radiologically (Grade III Kellgren and Lawrence classification[]) tricompartmental degenerative knee arthritis was appreciated []. Preoperative Kujala score[] was 49.\nWith patient in supine position under epidural anesthesia, an anterior midline knee incision was used with paramedian arthrotomy. The lateral retinaculum was thickened while the medial retinaculum was thinned. The lateral tether is released by dividing the fibrous adhesions, which extended along the lateral intermuscular septum. The lateral patellar retinaculum and the synovium were divided and vastus lateralis was detached from the quadriceps tendon, leaving a rim of tendon for suturing.\nDue to shortening of the extensor mechanism, the patella could not be reduced. Quadriceps tendon was lengthened using V Y plasty at aponeurotic junction. Tracking was augmented with MPFL reconstruction using semi-tendinosus tendon and patellar end was fixed with 2.8 mm FASTak titanium anchor on the medial border of patella and over near isometric point on medial epicondyle of femur, which was checked under fluoroscopy. Patellar maltracking was persistent and so, it was decided to proceed with medial and distal transfer of tibial tuberosity.\nA long-leg hinged knee brace was applied with the knee in 20° of flexion and partial weight bearing with crutches for four weeks was advised, during which the patient was encouraged to do vigorous static quadriceps strengthening exercises. Knee mobilization and full weight bearing was started after four weeks. Initially patient had extensor lag of 15 degrees as she was immobilized in flexion. But after vigorous quadriceps exercises, patient improved without any extensor lag.\nAt final followup two years postoperatively, the patient was pain-free. There was no evidence of patellar maltracking or instability on detailed physical examination. Radiographs showed well reduced patella in both lateral, anteroposterior view and skyline view []. The patient's kujala knee society score 89 [] and range of motion was 0° to 90° on the left side []. Quadriceps strength was rated 4 (MRC grade).
The patient was an 11-year-old Caucasian boy without any relevant familiar history or comorbidity. He referred to our clinic complaining disability in walking and running with frequent falls (due to the lack of power in knee extensor mechanism). His parents said that despite the absence of pain, the functional limitation of both his knees was at the base of a serious psychological discomfort, conditioning his relationship with peers.\nOn objective examination, his lower limbs revealed mild genu valgum and tibial proximal lateral torsion. Both patellae were on the lateral aspect of the femoral condyle displacing even further during knee flexion. Femoral quadriceps function was present but this muscle was working as a flexor instead of extensor of the knee. It was observed that he was unable to actively extend both knees from the flexed position; passive range of motion (ROM) was complete and was not painful. At the upper limbs, there was a mild deficit in ROM of both elbows. There were no pathological deviation of the spine; normal clinical finding of both feet. The anterior-posterior lateral and axial knee X-rays showed bilateral, superolaterally displaced and hypoplastic patellae and reduction of the trochlear groove (, , ).\nThe extensor mechanism was studied by magnetic resonance imaging (MRI): Both quadriceps were hypotrophic with the vastus medialis enveloped over the trochlear groove which appeared flattened and dysmorphic. The patellar tendons were bilaterally lateralized and stretched. The anterior cruciate ligament could not be identified. On both sides, MRI confirmed the lateral dislocation of the patellae ().\nElbows X-ray showed a slight posterior dislocation of the radial head and absence of radioulnar synostosis. The diagnosis of CDP was confirmed. Surgical correction of the deformity was then proposed to regain walking and running function, with the aim of reduce the grade of the deformity improving the patient quality of life and his psychological well-being.