The authors report 2 series of cases of rheumatoid arthritis, one prospective of 115 cases, the other retrospective of 72 cases, and note the frequency of clinical and radiological patellar and femoro-patellar involvement during this disease. Signs of active rheumatoid disease in the patella were present in 31 cases. The most common lesions of the femoro-patellar joint space are narrowing and lateral dislocation of the patella. The femoro-patellar lesions evolve in parallel to the femoro-tibial lesions, but dissociation is possible. The early detection of a femoro-patellar syndrome permits effective treatment by isometric rehabilitation of the quadriceps. On the most advanced lesions, and when pain is limited to the femur and patella, an operation of reaxation of the patella may provide remarkable functional improvement.