Measurement of the location of the medial meniscus (MM) on the coronal image of the MRI. A vertical line intersecting the peripheral margin of the medial tibial plateau (MTP) was drawn. Then, the second and third lines, which were parallel to the first line, were drawn at the outer and inner margins of the meniscus, respectively. The distance between the first and second lines, which was defined as “Extrusion width (EW)”, and the distance between the first and third lines, which was defined as “Inner width (IW)”, were measured. Each width was quantified in millimeters