Fig. 1.

Measurement methods of the patellofemoral joint. a Caton–Deschamps index (CDI) = T/P, where P is the patellar articular surface length and T is the distance from the anterior angle of the tibial plateau to the most inferior aspect of the patella articular surface. b Tilting angle (TA): the angle between the line intersecting the widest bony structure of the patella and the line tangentially passing the anterior surface of the femorl condyle. c Lateral patellar shift (LPS): the distance between the summit of the lateral femoral condyle and the point where a line from the lateral edge of the patella perpendicular to the line passes through the summit of the femoral condyles crosses that line. d Medial joint space/lateral joint space (MJS/LJS): most narrowed space of the patellofemoral joint. For LPS, MJS, and LJS, the value divided by the width of the patella (p) was also measured to correct the X-ray magnification (LPS/p, MJS/p, LJS/p)