The hip joint is formed by the head of the femur (thigh bone) and the acetabulum of the pelvis (a concave dome shaped area in the pelvic bone).
The labrum is also involved; it is a rim of cartilage around the acetabulum which deepens the joint to increase stability and ‘suctions’ the femoral head in to seal and protect the joint.
The hip joint is a ball and socket type joint, so allows a wide range of movement to occur.
It is given stability by muscles and ligaments which surround the joint and tighten at end range of movement.
Femoroacetabular impingement (FAI) occurs when the neck of the femur (the top part of the femur, just below the head) butts up against the acetabular rim, and can be caused by two types of impingement.
CAM impingement occurs when there is a structural abnormality of the femur, with excess bone at the femur head-neck junction.
Pincer impingement occurs when there is an abnormality of the acetabulum and excess bone. Both cause damage to occur to the labrum (it is a common cause of labral tears) and cartilage of the hip joint.
FAI is a chronic process that causes gradual and progressive degeneration at the area of impingement, and is a common cause of osteoarthritis of the hip.
It is very important to seek proper assessment and treatment so that the onset of hip osteoarthritis may be delayed or prevented.
Impingement is most likely to occur when the hip joint is moved into flexion and internal rotation (legs bent up and turned in).
Sports involving this hip position may increase the risk of developing FAI, such as hockey, tennis, soccer, water polo and weightlifting.
FAI most commonly occurs in young to middle aged adults, with males more commonly affected than females, and often in those who are active in sports.
Signs and symptoms
The primary symptom that people with FAI complain of is gradual onset progressive one sided groin pain, which may be aching, sharp or often both.
Pain location is not restricted to the groin however, it may present in other areas around the hip, such as the front or side of the hip. In some cases there may have been a history of minor trauma, but often there is not.
The pain is usually intermittent and is worsened by physical activity (often running or pivoting) or prolonged sitting.
Pain may be eased by rest and frequent changes of position.
X-rays, MRIs or CT scans may be needed to confirm a diagnosis of FAI.
Treatment and management
Physiotherapists can give advice on activity modification, use manual therapy techniques such as joint mobilisations, teach technique alteration for sports and give exercises to ensure muscles around the hip are balanced to alleviate and reduce pain.
This may be enough to effectively treat FAI; however some patients may require surgery.
Physiotherapy treatment is always recommended before considering surgery.
Surgery for FAI aims to increase the clearance between the femur and the acetabulum to stop the two structures from continuing to impact other.
This in turn stops the damage to the hip from continuing thereby alleviating pain and delaying osteoarthritis.
Physiotherapy post-surgery is important for assisting patients in regaining range of movement, mobility and returning to sport.
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