Femoroacetabular Impingement

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What is it?

Femoroacetabular impingement (FAI) is a condition where the bones of the hip are abnormally shaped. Because they do not fit together perfectly, the hip bones rub against each other and cause damage to the joint. The hip is a ball-and-socket joint. The socket is formed by the acetabulum, which is part of the large pelvis bone. The ball is the femoral head, which is the upper end of the femur (thighbone). The ball and socket needs to be perfectly round and correctly sized so that the ball and socket do not irritate and impinge each other. See figure 1 which shows a series of views where a comparison can be made between a normal ball and socket structure and those where abnormal bone structure will result in pain and discomfort during certain activity which causes impingement to occur.

Figure 1 provides a series of views of bone structures which are abnormally shaped within the ball and / or socket which can cause impinging and irritation to occur due to bone on bone contact.

How did I get it?

FAI occurs because the hip bones do not form normally during the childhood growing years. It is the deformity where extra bone growth / spur leads to damage and pain. When the hip bones are shaped abnormally, there is little that can be done to prevent FAI. Because athletically active people may work the hip joint more vigorously, they may begin to experience pain earlier than those who are less active. However, exercise does not cause FAI.

What are the symptoms?

People with FAI usually have pain in the groin area, although the pain sometimes may be more toward the outside of the hip. Sharp stabbing pain may occur with turning, twisting and squatting, but sometimes it is just a dull ache.

What should I do?

When symptoms first occur, it is helpful to try and identify an activity or something you may have done that could have caused the pain. Sometimes, you can just reduce your activities, let your hip rest, and see if the pain will settle down. Over-the-counter anti-inflammatory medicines (ibuprofen, naproxen) may help. If your symptoms persist, you will need to see a doctor to determine the exact cause of your pain and provide treatment options. The longer painful symptoms go untreated, the more damage FAI can cause in the hip.

How is a diagnosis made?

The diagnosis can be straightforward or very difficult depending on the nature of the symptoms. Many patients can be diagnosed easily based on the nature of the pain, physical examination and x-rays. Sometimes extra tests such as ultrasounds and MRI are performed to either eliminate other possible causes or confirm the diagnosis. In some circumstances there is significant overlap between FAI and other causes of hip and groin pain making diagnosis extremely difficult. In these cases injections may be necessary. An injection of local anaesthetic (like you have when you have a mole removed) will make the area numb and remove pain. In the clinic you may be asked to perform an activity that you find provocative before and after an injection. If the provocative activity is not painful after the injection it greatly increases confidence in the diagnosis.

What does rehab involve?

Activity modification: Simply changing your daily routine and avoiding activities (or performing them differently) that cause symptoms. Avoiding deep squatting and exercises that have the knee cross the body may be enough to allow the hip to settle down. It will be important not to force hip stretches. If there is bone impinging on bone then trying to push through the stretch (as you might for a tight muscle) will only cause the bones to further impinge and exacerbate the condition.

Non-steroidal anti-inflammatory medications: Drugs like nurofen and voltaren can reduce pain.

Physical therapy: Specific exercises can improve the range of motion in your hip and strengthen the muscles that support the joint. This can relieve some stress on the hip joint.

Hip joint injections: In mild cases of disease or in the event of a flare of symptoms an injection may be useful to settle or control the pain.

Surgery: Sometimes surgery is required for FAI to trim the excessive bone back so that impingement does not occur. However, this is a last resort.


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