The hip is one of the most dynamic joints in the body. Much like the shoulder joint, the hip grants us the ability to perform many different activities from simply getting out of a chair to more complex ones such as playing tennis or participating in ironman triathlons. In addition to the wide range of motion afforded by the hip, it also helps to keep us upright as a weight-bearing joint. All of this utility does come at a cost over time and the hip, as with any joint in the body, is subject to osteoarthritis and myriad pathologies that can significantly affect one’s day-to-day activities and well-being.
The hip is a ball-in-socket joint comprised of the head of femur (ball) that articulates with the acetabulum (socket). The femoral head is angled away from the acetabulum in such way that it allows for greater leverage to support the upper body. The acetabulum is formed by the union of the ilium, ischium, and pubis (Figure 1). Much like the rotator cuff of the shoulder, movement of the hip joint is made possible by a similar group of muscles. These muscles act to facilitate movement in all planes of motion and, unlike the shoulder muscles, provide enough stability to the joint to support up to six times our body weight with activity.
Attached to the bony rim of the acetabulum is a continuous fibrous cartilage known as the labrum (Figure 2). The labrum is a sensitive shock absorber, seals the synovial fluid that lubricates the joint, and aids in distributing pressure evenly within the joint space. It also stabilizes the hip laterally and vertically, deepens the acetabulum and increases its surface area to distribute load and decrease stress on articular surfaces.
Labral tears can be caused by an acute traumatic injury or the result of chronic degenerative changes over time. The former mechanism usually involves resistance to forced hip flexion, such as when an athlete is kicking or running. The latter mechanism is most often the result of repetitive micro trauma in the setting of osteoarthritis. Conversely, labral tears often lead to joint instability, which hastens progression of arthritis in the joint. The anterior (front) portion of the labrum receives the least amount of blood compared to other portions and is subject to the greatest amount of pressure from the femoral head. As a result, this is the most common area where labral tears will happen. Posterior tears are more common in those who regularly perform activities that require repetitive squatting, which cause the femoral head to move backwards.
Symptoms of labral tears are similar to those of osteoarthritis (groin pain, stiffness), with a few distinguishing characteristics. Tears of the labrum may cause clicking, locking or “giving way” when bearing weight on the affected hip. A clinical exam might reveal a positive anterior hip impingement test. Evaluation begins with plain x-rays to assess for other causes of pain and usually requires MRI arthrography to confirm. Initial management of labral tears involves rest from activity and physical therapy to strengthen the muscles surrounding the joint. If conservative management fails, your physician may refer you to an orthopedic surgeon to undergo arthroscopic repair.
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