Figure 15.

A frog lateral view of the right hip: A, the cam lesion (arrow) is evident as the convex abnormality at the head–neck junction, where there should normally be a concave slope of the femoral neck; B, the alpha angle is used to quantitate the severity of the cam lesion. A circle is placed over the femoral head. The alpha angle is formed by a line along the axis of the femoral neck and a line from the center of the femoral head to the point where the head diverges outside of the circle (arrow).