The patellar resection angle (a-b), patellar tilt (b-c), and femoral component rotation angle (c-d) were measured on plain axial radiographs. a: a line at the anterior patellar cortex connecting the ends of perpendicular lines drawn at the medial and lateral aspects of the patella, b: patellar resection axis, c: anterior condylar axis, d: surgical transepicondylar axis.