Abstract
A 75-year-old woman presented with progressive bilateral knee pain and severe genu valgum. She could walk utilizing braces and T-canes, with a 20° flexion contracture and 150° of maximum flexion. During knee flexion, the patella laterally dislocated. Radiographs demonstrated severe bilateral lateral tibiofemoral osteoarthritis and patellar dislocation. She underwent posterior-stabilized total knee arthroplasty without patellar reduction. After implantation, the knee range of motion was 0°-120°. Intraoperative findings revealed that the affected patella was too small, low articular cartilage volume resulted in the diagnosis of nail patella syndrome with the tetrad of nail dysplasia, patella dysplasia, elbow dysplasia, and iliac horn. At the 5-year follow-up visit, she could walk without a brace and had a knee range of motion (10°-135°) with clinically favorable results.