Femoroacetabular impingement (FAI) occurs due to pathology between the femoral head and neck junction. Two types of FAI have been described: cam and pincer.
Cam FAI is an out of round spherical head, caused by a bone metaplastic overgrowth at the head-neck junction that damages the articular cartilage from the overload and shear as it rotates into the acetabulum. Softening and blistering of the anterior acetabular articular cartilage to degeneration and tearing of the labrum occurs with progressive stages.
Pincer FAI occurs with acetabular overcoverage which limits ROM and leads to the labrum impacting the femoral neck.
FAI affects men and women equally beginning the second and third decades of life with subsequent progression. Pts present with pain in the groin. At times the pain is associated with a popping or catching sensation. Xrays can demonstrate a lateral femoral neck prominence, rim overgrowth, fibro-osseous cysts. Intraarticular contrast MRI with a diagnostic anaesthetic assists with confirmation of the diagnosis.
Conservative involves limitation of activities, NSAIDS, and physical therapy. Arthroscopy can be helpful in the earlier stages before progression to osteoarthritis.