Fig. 2A–C.

(A) The sulcus angle (SA) is the angle between the medial and lateral trochlear facets. (B) Lateral and medial trochlear inclination is the angle between the posterior condylar line and a line along the lateral and medial facets, respectively. (C) The trochlear angle is the angle between the posterior condylar line and a line passing along the most anterior margin of the medial and lateral trochlear facets. (Published with permission and adapted from Stefanik JJ, Roemer FW, Zumwalt AC, Zhu Y, Gross KD, Lynch JA, Frey-Law LA, Lewis CE, Guermazi A, Powers CM, Felson DT. Association between measures of trochlear morphology and structural features of patellofemoral joint osteoarthritis on MRI: the MOST study. J Orthop Res. 2012;30:1–8. Copyright 2012 Wiley.)