A study of congruity of the patellofemoral joint was made on 31 cases (51 joints) of total knee arthroplasty (Miller-Galante type) which were performed from 1986 to 1989. There were 5 males and 31 females. Their mean age was 70.5 years and their ages ranged from 37 years to 82 years. 24 cases (35 joints) were gonarthrosis and 12 cases (16 joints) were rheumatoid arthritis. These were 2 cases (2 joints) of luxation, 3 cases (3 joints) of subluxation and 7 cases (9 joints) of lateral tilt. The causes of luxation were unbalance of soft tissue, increase of Q-angle and design of the femoral component. The patella of the M-G type has tendency to luxation due to small anterior flange and shallow patellar groove of the femoral component. Therefore, the soft tissue balancing at the time of operation was more important in the M-G type than in the other types of total knee arthroplasty.
