What is Femoroacetabular Hip Impingement?

Femoral acetabular hip impingement can occur as a result of subtle structural variances within the bony anatomy of the hip. When these variances are present they can cause pain and impingement

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Femoral acetabular hip impingement can occur as a result of subtle structural variances within the bony anatomy of the hip. When these variances are present, the acetabulum and the femoral head and neck can come into contact with each other, causing pain and impingement (Hendry et al., 2013).

There are two key structural (bony) changes associated with femoral acetabular hip impingement. These are as follows;

Cam lesions – this refers to an excess of bone located on the head/neck of the femur. As the hip moves this excess of bone can impact with the acetabulum, causing a bony pinch or ‘impingement’.
Pincer lesions – this refers to an excess of bone located on the rim of the acetabulum. Once again, as the hip moves, this bony protuberance catches on the femoral head/neck causing direct injury to the femur. Hip joint pathology can also occur at the opposite side of the joint due to a lever-action caused by the pincer lesion.
It is not uncommon for some patients to experience both Cam and Pincer lesions at the same time (Cheatham et al., 2016).
Femoral acetabular impingement is a common cause of hip pain in both young and middle-aged patients and has been associated with the development of secondary hip osteoarthritis (Park et al., 2012).

Load-bearing joints such as the hip and knee are the most commonly affected by osteoarthritis [cornerstone hip article]. Current research has shown that articular cartilage requires good quality joint movement to maintain its health. Inappropriate movement patterns or sustained suboptimal loading can cause the articular cartilage to become thinned and compromised (Clarke et al., 2003). The process results in the degenerative process known as osteoarthritis.

Fortunately, research has also demonstrated that maintaining good flexibility and strength around the joint will help to slow the disease progression associated with osteoarthritis (Hunter et al, 2009).

Cheatham et al., (2016) states that the development of femoral acetabular impingement is mainly congenital. However, there are a number of risk factors associated with femoral acetabular impingement (FAI). These include;

• Hip joint hypomobility (reduced range of motion)
• Muscular stiffness/tightness in surrounding hip musculature
• Suboptimal gait pattern (differences in the way you walk have been observed in patients with FAI)
• Hip muscle weakness is regularly noted in patients with FAI (46% of FAI patients have been shown to exhibit weakness in the lateral gluteal muscles, used to stabilise the hip joint)
• Changes in the position of the pelvis have also been observed in patients with FAI
• The chance of FAI is increased after hip fracture