Fig. 4

The patella tilt angle \(\delta\) (a) was measured between the reference line (G) at the posterior femoral condyles and a line going through the medial and lateral edges of the patella at the level of the maximal width. The PL-T distance (b) was measured by drawing a line perpendicular to the reference line (G) which projects anteriorly through the most anterior point of the lateral trochlear facet. The distance between the dorsal aspect of the ligament and the ventral aspect of the lateral trochlear facet cartilage was measured. The patellar height is assessed with the ISR (c) which is defined by the ratio of the patellar tendon length (A) to the length of the patella (B). ISR, Insall‒Salvati ratio; PL-T, patella ligament to trochlear distance