Hip Joint Anatomy And Femoroacetabular Impingement
The hip joint is what is known as a ball and socket joint. The “socket” part of the hip joint is called the acetabulum, the acetabulum is part of the large pelvis, and this socket is actually made up of all three of the pelvis bones (the ilium, ischium and the pubis). The “ball” component of the ball and socket joint is the femoral head, the femoral head is the upper end of the thighbone known as the femur. Both these ball and socket surfaces the acetabulum and femoral head are covered in articular cartilage, Articular cartilage is a hard, slippery tissue that creates a strong and smooth, low friction surface assisting the bones of the ball and socket joint to repeatedly glide and slide easily against each other under significant loads without damaging the bones. The socket of the hip is further cushioned and stablised through a strong fibrocartilage wedge called the labrum. This labrum runs around the entire socket, like a protective seal around the rim of a teacup, helping create a tight seal around the joint, stability and additional cushioning to the hip joint. Femoroacetabular Impingement being the bit of a mouthful that it is, is often abbreviated to FAI, or simply referred to as hip impingement syndrome. Femoroacetabular Impingement refers to a situation where the spherical femoral head and matching socket abut abnormally against each other in some capacity. This means that an individual’s normal range of motion is not permitted without the ball and socket “pinching” in some way. With these bony surfaces abutting against each other it means that certain movements and activities over time may lead to labral damage, articular cartilage damage and other bone and soft tissue changes around the hip joint. These changes given time in some individuals may ultimately lead to functional limitations and discomfort. In some circumstances FAI will lead to hip osteoarthritis and necessitate a total hip replacement.
Types Of Hip Impingement
There are 3 types of hip impingement. One of these exclusively involves the socket, another the femoral head and the other is a combination of both. Listed below are the 3 types of FAI:
- Cam Impingement: With a Cam hip impingement the femoral head is abnormally shaped. The normally spherical head has changed, and this non-spherical head no longer rotates within the socket in its typical smooth fashion. Cam deformities are characterised by extra bone formation on the edge of the femoral head-neck junction and as such this bony formation can “grind” at the cartilage of the hip socket.
- Pincer Impingement: A pincer version of hip impingement occurs where “extra” bone extends out over the rim of the hip socket. In this pincer hip impingement situation, the labrum can become “crushed” under the prominent rim of the hip socket. This stress on the labrum can potentially be a source of pain.
- Combined Impingement: A combined impingement is exactly that, it simply means there is a situation where both Cam and Pincer type changes at the hip exist.
FAI Is A Major Risk Factor For Osteoarthritis
Clearly this all sounds very dramatic and scary, particularly if you have Dr Googled yourself as having FAI. The good news is that many people with subjective and objective signs of hip impingement will respond to nothing more than some simple activity modification. A few adjustments to their training, or lifestyle behaviors can often prove enough to avoid the process progressing beyond anything more than some transient discomfort.
However, with femoroacetabular impingement bony overgrowth developing around the hip joint at the femoral head and/or along the acetabulum as mentioned can impact the hip joints ability to fit and move together. As such abnormally spurred surfaces can pinch, jam, rub (insert whatever verb you want to use here) causing damage to joint structures like the articular cartilage and labrum. It has been shown that young adults having undergone a hip arthroscopic surgery for FAI are found to have a hip joint that hip demonstrates signs of joint disease, early signs of hip osteoarthritis.
One of the impingement types listed above, a Cam deformity has specifically been identified as being a major risk factor in the development of end stage hip osteoarthritis.
Physiotherapy And Femoroacetabular Impingement
FAI is often seen as a surgical problem, many patients with a diagnosis of hip impingement visit an orthopaedic surgeon both seeking relief and answers. Surgery as a management in chronic hip impingement is often a very effective solution, at least temporarily. However, it should me mentioned that physiotherapy too can play pivotal role in the successful management of
hip impingement related pain. It is not uncommon to utilize more conservative approaches including activity modification, targeted strengthening, stretching exercises, as well as appropriate manual techniques to provide relief to some of the discomfort and improve function. An understanding of the condition and what postures, movements and activities may irritate and conversely what can be potential beneficial can go a long way to managing mild to moderate hip impingement associated discomfort.
Imaging and orthopaedic assessment is frequently useful to gauge the type of impingement, severity, monitor change over time and assist in long term goal setting and any necessary lifestyle changes needed. However, from a physiotherapy preference, only if conservative measure fail to achieve desirable results, or the impingement is contributing to articular cartilage changes would surgery be the option of choice. But because once articular changes have set in they often start a process of osteoarthritis within the joint having a specialist involved is a safe option to avoid regret down the track.
