The hip joint is a ball and socket joint. Femoroacetabular Impingement (FAI) or 'Hip impingement' is a condition where the femoral head (ball) or the acetabulum (socket) do not fit together normally because of an abnormality in the shape in one or both of these body parts. The result is increased friction during hip movements that may damage the hip joint. Impingement is the premature and improper collision or impact between the head and/or neck of the femur and the acetabulum. This causes pain and decreased range of motion of the hip joint.
FAI can occur as a result of excess bone or bump around the femoral head-neck junction (CAM impingement) or due to overgrowth of the acetabular rim (Pincer impingement) or due to combination of both. Sometimes impingement can occur because the socket is angled in such a way that abnormal impact occurs between the femur and acetabular rim.
Repetitive collisions between the bones such as in athletic activities involving repeated hip flexion, can result in injury to the soft tissues of the hip, especially the labrum (soft rim of cartilage around the edge of the socket) and the true joint cartilage, and eventually leading to osteoarthritis.
Patients present with pain in the front of their hip (groin) after prolonged sitting or walking. The pain can be a consistent dull ache, with intermittent sharp episodes if there is an associated labral tear. Mechanical symptoms such as a catching and/or sharp, popping sensation are also common. The pain can radiate along the side of the thigh and in the buttocks.
Diagnosis is made on the basis on clinical examination, X-rays and MRI scan. An MRI can also reveal any damage to the labrum and cartilage.
Patients with minimal symptoms and no mechanical symptoms can be treated non-surgically, with rest, anti-inflammatory medications, modifying one’s behaviour and physiotherapy.
If pain persists, a steroid injection into the hip joint can be considered to as a diagnostic tool or to provide some symptomatic relief.
Hip arthroscopy (keyhole) is the gold standard for treating hip impingement in patients with persistent symptoms. Hip arthroscopy is usually contraindicated in patients > 55 years of age and if there are signs of advanced osteoarthritis. A total hip replacement is recommended as a last resort in such patients.