Femoroacetabular impingement is characterized by abnormal contact between the proximal femur and rim of the acetabulum. It affects typically healthy, active adults, between 25 and 50 years. Cam lesions are more common in young males.

Cam impingement is a result of a non-spherical head causing abnormal contact stresses.

In most cases, the proximal femoral malformation is idiopathic. It also can be a sequela of childhood disease, including SCFE or any hip in which the femoral neck is too large.