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Hip pain can be misdiagnosed.

Posted Feb 15 2010 4:11am

A patient of mine was recently referred to an orthopedist because of hip pain that I could not help. She was then diagnosed with a condition called Femoroacetabular impingement or FAI. This is a condition of too much friction in the hip joint. Basicallythe ball (femoral head) and socket (acetabulum) rub abnormally creating damage to the hip joint. The damage can occur to the articular cartilage (smooth white surface of the ball or socket) or the labral cartilage (soft tissue bumper of the socket).

FAI generally occurs as two forms: Cam and Pincer. The Cam form (Cam comes from the Dutch word meaning “cog”) describes the femoral head and neck relationship as aspherical or not perfectly round. This loss of roundness contributes to abnormal contact between the head and socket. The Pincer form (Pincer comes from the French word meaning “to pinch”) describes the situation where the socket or acetabulum has too much coverage of the ball or femoral head. This over-coverage typically exists along the front-top rim of the socket (acetabulum) and results in the labral cartilage being “pinched” between the rim of the socket and the anterior femoral head-neck junction. The Pincer form of the impingement is typically secondary to “retroversion”a turning back of the socketor “profunda”a socket that is too deep. Most of the timethe Cam and Pincer forms exist together.

FAI is associated with cartilage damagelabral tearsearly hip arthritishyperlaxitysports herniasand  low back pain. It is common in high level athletesbut also occurs in active individuals. While the cause of the back pain is not well understoodthe pain is often localized to the SI (sacroiliac joint on back of pelvis)the buttockor greater trochanter (side of hip). FAI pain typically does not go beyond the level of the knee.
The diagnosis can be straightforward or a diagnosis of exclusion. Most patients can be diagnosed with a good historyphysical examand plain x-ray films. A patient’s history will generally involve complaints of hip pain (frontsideor back) and loss of hip motion. The physical exam will generally confirm the patient’s history and eliminate other causes of hip pain. The plain x-ray films are used to determine the shape of the ball and socket as well as assess the amount of joint space in the hip. Less joint space is generally associated with more arthritis.

Often an MRI of the hip is used to confirm a labral tear or damage to the joint surface. The MRI is most helpful in eliminating certain causes of non FAI hip pain including avascular necrosis (dead bone) and tumors.

This condition can be treated conservatively; howeverit involves a change in lifestyle from active to less active and a commitment to maintaining hip strength. Non-operative management may not change the underlying abnormal hip biomechanics of FAI. If surgery is advisedyour orthopedist will discuss the options for you. I always advise my patients to try conservative care first before doing more invasive procedures.

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