The anatomy of the hip has many variations. In some cases, there may be excessive bone at the head/neck junction of the femur, often referred to a CAM lesion, or excessive extension of the rim of the acetabulum, known as a PINCER.
Femoroacetabular impingement (FAI) may occur with either of these anatomical issues and is basically contact of the bony and soft tissue structures at the extremes of hip motion. Over time and as a result of repetitive contact, this may lead to pain and a variable amount of damage to the joint structures, including the cartilage at the rim of the socket and the acetabular labrum. It is a condition which frequently affects active people.
In the absence of significant joint degeneration, the symptoms of FAI can be treated surgically. In the vast majority of cases this can be done with hip arthroscopy to reshape the bone and address the labral damage.