Minimum Four-year Results in Patellar Components after Total Knee Arthroplasty

15 TKAs observed more than 4 years were examined for changes in the patellar position with the time. The patellar height and patellar tilt were measured by preoperative roentgenograms and postoperative roentgenograms at 4 weeks and more than 4 years, The range of motion (ROM) of the knee was compared with the measured value. 15 TKAs were classified into 2 groups by the ROM. 8 TKAs with ROM greater than preoperation were group A and 7 TKAs with ROM less than preoperation were group B. The average index of the patellar height in group B was 0.99 prior to operation, 1.01 at 4 weeks after operation, 0.83 at more than 4 years. Each was 1.001, 1.06, 0.97 respectively in group A. The patellar height showed a temporary high average after operation, but showed low at more than 4 years. The average tilting angle in group B was 5.9° prior to operation, 9.7° at four weeks, 9.3° at more than 4 years. Each 3.3°, 5.2°, and 6.0° respectively in group A.