Fig. 1 A-C.

Patellar-to-trochlear width ratio was calculated from the 3-D model. (A) The point of transition from anterior to posterior cartilage on the medial and lateral femoral cartilage extremes (med cart and lat cart, respectively) were located on the bone within the MR images using the 3-D viewing tool in MIPAV (NIH, Bethesda, MD, USA). (B) These medial and lateral transition points from the static images were transferred to the 3-D bone model. A coronal plane (cor_cut plane), relative to the imaging coordinate system, was then rotated about the imager’s superoinferior axis until it contained the mediolateral transition points. This defined the oblique coronal cut plane. (C) This cutting plane was translated anteriorly and used to trim the most anterior sections of the lateral and medial femoral condyles. The center of these regions (anterolateral [AL] and anteromedial [AM]) defined the trochlear width (TW). Patellar width (PW) was calculated as the mediolateral distance using a bounding box. This bounding box was defined relative to the imaging coordinate system.