Hip Impingement

The hip is a ball-and-socket joint. In a healthy hip, the femoral head, which is the ball at the end of the femur, rotates within the acetabulum, the socket in the pelvis.


The femoral head is kept in place by a layer of fibrocartilage known as the labrum and a thin layer of tissue known as articular cartilage. The femoral head and the acetabulum work to keep bones rotating smoothly. Hip impingement, also known as Femoroacetabular (FAI), is a condition in which the bones of the femoral head or acetabulum are abnormally shaped and may rub against each other, damaging the joint. People with FAI typically experience sharp pains or dull aches when turning, twisting or squatting.

There are three forms of this condition: pincer, cam, and combined impingement. Pincer impingement happens when the bone of the acetabulum extends further than usual which could crush the labrum. Cam impingement occurs when the bone of the femoral head is not round and it grinds against the articular cartilage. A combined impingement is a combination of both pincer and cam impingements.

A diagnosis of FAI is typically made by a physician, using a combination of medical history, physical examination of the hip, and imaging studies including X-ray, MRI and CT scan. 

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