The hip joint is a ball and socket joint formed between the head of the femur (thigh bone) and the acetabulum of the pelvis (the socket). There are individual variations in the anatomy of both the ball and the socket that can lead to a condition called femoroacetabular impingement (FAI), which causes hip pain in some people. The socket of the hip joint is made deeper by a fibrocartilage rim called the labrum. This is responsible for creating a seal in the hip joint to help keep the synovial fluid in the centre of the joint, which enhances stability of the joint and provides protection to the cartilage. Tears to the labrum can cause pain in the hip and also predispose to the development of osteoarthritis of the hip joint. The hip joint is also susceptible to two specific conditions affecting the bone of the femoral head causing pain and disability – avascular necrosis and transient osteoporosis.
Femoroacetabular impingement (FAI)
FAI is caused when there is an abnormal anatomical relationship between the ball and socket of the hip joint. This causes impingement of the bones and soft tissues in specific positions of the hip, particularly in flexion. There are 2 types of FAI – cam and pincer type deformities and they can also occur together. Cam deformity is a non-spherical head of femur (ball of hip joint) with an abnormal head-neck offset that creates compressive and shear forces during hip flexion. Pincer deformity is over coverage of the femoral head by the acetabulum (a deeper than normal socket).
Cam deformity can be present in up to a quarter of the population and cause no pain. It’s much more common in males than females and has a very high prevalence in athletic males (found in 89% of athletic males in one study compared to 9% of non-athletic males of the same age). Pincer deformities are more common in females. Only about a quarter of people who have a cam deformity (found on x-ray) complain of associated hip pain. FAI is the condition experienced when someone has pain due to a cam or pincer deformity.
The condition is diagnosed using a combination of clinical examination and imaging. Often the pain is worse with prolonged sitting in a position with more than 90 degrees of hip flexion. This may lead to hip pain during sport and/or leisure activities. It is managed initially by resting from aggravating activities and a comprehensive rehabilitation program to correct strength and mobility imbalances in the pelvis, core and lower limbs. Surgery to correct the deformity may be needed in some cases to relieve pain. FAI may also be associated with labral tears.
Labral tears can cause hip and groin pain but there is also a significant portion of the population who have labral tears with no symptoms (they are picked up on imaging which is performed for a different reason). Labral tears can be associated with FAI or with developmental dysplasia of the hip (see hip conditions in children and adolescents). Someone with a labral tear is 40% more likely to have an injury to the cartilage of the hip joint as well.
The diagnosis is made using a combination of clinical examination and imaging (MRI). The person might complain of mechanical symptoms such as locking, clicking, catching or giving way as well as their hip pain. Pain may be triggered by jumping or sprinting or at the end of a long run when fatigue sets in. Non-surgical management should be trialed before surgical intervention is pursued. This can be using a combination of rehabilitation and injections if indicated. There are numerous surgical options if non-operative management fails and most people experience short-term relief after arthroscopy.
This is a condition that causes compromise of the blood supply to the femoral head (ball of the joint) that leads to death of the bone cells and marrow and mechanical failure of the bone. The process can progress quickly over a few months or slowly over a few years. It can be related to trauma, alcohol intake or glucocorticoid use.
It can present as hip or groin pain that is worse with weight bearing or motion. Two thirds of people also have pain at rest and one third have pain at night. There is usually reduced range of motion of the hip. Diagnosis is made with clinical examination and imaging. Management aims to preserve the joint for as long as possible. Non-operative management often fails and many end up needing surgical management of which a total hip replacement is the definitive procedure.
It is unknown why some people suddenly develop osteoporosis confined to their hip joint but it may be related to trauma or changes to the blood and nerve supply of the bone. The condition presents in three stages – initially there is a rapid increase in hip pain and disability for 1-2 months, then symptoms plateau for 2-3 months but signs can now be seen on x-ray, and the third stage signals a gradual resolution of symptoms after 6 months but x-ray changes can persist for longer.
The condition mainly affects healthy middle-aged men and healthy women in their third trimester of pregnancy. X-rays of the hip show diffuse demineralisation of the bone and MRI of the hip can distinguish between the changes in the femoral head from avascular necrosis and transient osteoporosis. The condition is self limiting and will resolve completely with time but it is important to reduce the risk of fracture of the hip during the time the osteoporosis is present and crutches may be needed to offload the joint when symptoms are present.
If you have sustained a hip injury that has resulted in significant pain or a limp, or you can no longer participate in your preferred activity due to hip pain, a consultation at Shire Sports Medicine can be beneficial for you to get an accurate diagnosis, to help guide management of your condition and to ensure the prevention of further complications.