Femoroacetabular impingement (FAI) is a condition involving one or more anatomical abnormalities of the hip joint, which is a ball and socket joint. It is a common cause of hip pain and discomfort in young and middle-aged adults. It occurs when the ball shaped femoral head contacts the acetabulum abnormally or does not permit a normal range of motion in the acetabular socket. Damage can occur to the articular cartilage, or labral cartilage (soft tissue, ring-shaped bumper of the socket), or both. The condition may be symptomatic or asymptomatic. It may cause osteoarthritis of the hip. Treatment options range from conservative management to surgery. Signs and symptoms
Pain is the most common complaint in those with FAI. It is experienced in a number of areas, making the diagnosis challenging, but commonly occurs in the groin, upper buttock/lower back, the buttock or beneath the buttock, side of the affected hip and posterior upper leg. Onset of symptoms has been reported to present in both an acute and more gradual manner. The pain is often significant enough to cause a decrease in activity level and movement. Some will also describe decreased range of motion of the affected hip. Another symptom is groin pain associated with activity and no prior history of trauma. Inability to perform activities such as high hip flexion or prolong sitting can also be seen in individuals with FAI. Cause
FAI is characterized by abnormal contact between the proximal femur and rim of the acetabulum (hip socket).
Differential Diagnosis
Piriformis syndrome or strain
Labral tear without FAI
Adductor muscle strain
Sciatica
Athletic pubalgia
Gluteus medius/minimus or illiopsoas tendinopathy
Stress fracture
Femoral head osteonecrosis
Other impingements, including anterior inferior iliac spine, ischiofemoral and iliopsoas
Loose body in the joint (intra-articular body)

Prevention
Prevention is currently being investigated. The goal of prevention would be to avoid joint damage and premature hip osteoarthritis. Studies are examining the effectiveness of screening adolescents in school and targeting at-risk individuals for education, physical therapy and decreasing participation in possibly harmful activities/sports as referenced in the epidemiology section. Treatment
Treatment of FAI can be divided into those that are non-operative (conservative) and operative. Conservative treatment is often prescribed for those who have not yet received any therapy. Conservative treatment includes physical therapy, avoidance of those activities that produce pain, and  nonsteroidal anti-inflammatory drugs. It may also include joint injections with cortisone or hyaluronic acid, particularly for those who wish to avoid surgery.Physical therapy is implemented for the purpose of improving joint mobility, strengthening muscles surrounding the joint, correcting posture, and treating any other muscle or joint deficits that may be exacerbating the condition. A movement analysis may also be performed to identify specific movement patterns that may be causing injury. Studies to demonstrate the effectiveness of physical therapy are currently underway, with no conclusive results to date.Operative treatment is generally recommended to those who continue to have symptoms. It involves the surgical correction of any bony abnormalities causing the impingement and correction of any soft tissue lesions, such as labral tears.