FAI impingement generally occurs as two forms: Cam and Pincer. The Cam form of impingement is when the femoral head and neck are not perfectly round, most commonly due to excess bone that has formed. This lack of roundness and excess bone causes abnormal contact between the surfaces. The Pincer form of impingement is when the socket, or acetabulum rim, has overgrown and is too deep. It covers too much of the femoral head resulting in the labral cartilage being pinched. The Pincer form of impingement may also be caused when the hip socket is abnormally angled backwards, causing abnormal impact between the femoral head and the rim of the acetabulum. Most diagnoses of FAI include a combination of the Cam and Pincer forms. The femoral head and acetabulum rub against each other, creating damage and pain to the hip joint. The damage can occur to the articular cartilage (the smooth white surface of the ball or socket) or the labral tissue (the lining of the edge of the socket) during normal movement of the hip. The articular cartilage labral tissue can fray or tear after repeated friction. Over time, more cartilage and labrum are lost until eventually the femur bone and acetabulum bone impact on one another. Bone on bone friction is commonly referred to as osteoarthritis. A risk factor is something that is likely to increase a person’s chances of developing a disease or condition. Risk factors for developing femoroacetabular impingement may include the following: - Athletes such as football players, weightlifters, and hockey players - Workers engaged in heavy labor - Repetitive hip flexion - Congenital hip dislocation - Anatomical abnormalities of the femoral head or angle of the hip - Legg-Calves-Perthes disease: a form of arthritis in children where blood supply to the bone is impaired, causing bone breakdown. - Trauma to the hip - Inflammatory arthritis