The hip joint is a very strong, stable ball-and-socket joint. The femoral head or ball-shaped upper portion of the femur (thighbone) articulates with the “socket” of the pelvis, also known as the acetabulum. The acetabulum is made up of the iliac, pubic, and ischial bones of the pelvis. Cartilage, which protects and cushions the bones while in motion, covers the hip joint. A lining surrounds the hip joint and provides synovial fluid, a moisturising lubricant. Ligaments hold the bones of the joints together and muscles and tendons add more stability.
However, the hip is prone to a number of problems:
- The bones and joints deteriorate over time. The cartilage, the smooth lining that covers the hip joint, breaks down, causing the underlying bones to wear against each other, resulting in severe pain and stiffness known as osteoarthritis.
- Rheumatoid arthritis attacks and destroys the lubricating synovial lining of the joint capsule (a saclike structure enclosing the end of the bone) and cartilage of the joint, causing pain, swelling and immobility.
- The narrow neck of the thighbone (femur) can break. This is usually what happens when an older person falls and breaks a hip due to osteoporosis.
- The “ball” part of the femur must get its blood through the narrow neck that joins with the pelvis. The small artery that supplies the head of the femur can close off, leading to death of the bone and a type of arthritis.
The most common causes of hip pain are injuries. However, the list of causes of hip pain is extensive and includes many rare ailments. For example, Legg-Calve-Perthes disease affects 1 in 1 000 children between the ages of 5 and 10 years and might result in the destruction of the growth plate in the neck of the thighbone. A few of the more common causes of pain not related to injury include:
- Forms of arthritis – including osteo- and rheumatoid arthritis, lupus and gout
- Bursitis of the hip – pain sets in slowly over time and is caused by overuse of the joint. Pain is felt on the outside of the hip over the thigh bone, just under the skin.
- Aseptic necrosis – caused by a clogged artery at the head of the femur, secondary to excessive alcohol intake and steroid therapy, amongst many other causes.
- Joint infection – for example septic arthritis
- Viral illnesses – especially influenza, which can cause muscle and joint ache and pain
- Muscle cramps – may have no clear cause, or may be due to dehydration or failing to stretch before exercise
Hip pain is often felt in the middle of the thigh, groin or same-side knee, whereas low back pain is often felt in the region of the buttock. Because the hip joint is so deeply located, it can often be difficult to locate the exact source of the pain.
Because hip pain is a symptom of so many ailments, it affects children, the aged, and men and women alike.
Depending on the cause, pain onset can be rapid or slow. Often it can be treated at home with rest and medication. In other cases, surgery will be required.
Due to the prevalence of osteoarthritis-related hip pain, the aged are more at risk of suffering hip pain. In addition, the frail run an increased risk of falling and injuring the hip joint. Rheumatoid arthritis, on the other hand, attacks both young and old, and more women than men.
When to see a doctor
Call your health care provider if:
- You know your hip pain is caused by injury
- Pain is severe and you can think of no injury or activity that might have caused it
- Pain persists after two weeks of home treatment
- Pain is accompanied by an unexplained fever, or becomes more severe or frequent
- The hip is unable to bear any weight, or if walking is impossible
Make a note of when the pain occurs, what you are doing when it occurs, and if it seems to occur after a specific amount of exercise or after walking a specific distance. Describe any home treatment you have tried. If you have had similar symptoms before, tell your doctor.
In order to make a diagnosis, your doctor will enquire about your medical history. He or she will ask questions about:
- Is the pain symmetrical (in both hips)?
- Does the pain migrate (shift from the hip to other joints)?
- Is the pain in the hip as well as the thigh?
- Did the symptom begin suddenly, or slowly and mildly?
- Did the symptom resolve spontaneously in less than six weeks?
- Did the hip pain begin after an injury or accident?
- Did the pain begin in the hip?
- Did the pain begin in the back and then radiate to the hip?
- How severe is the pain?
- What other symptoms are present?
- Can you walk?
A physical examination will include particular attention to the hip and its range of motion. X-rays of the hip may be necessary to exclude the possibility of bone fractures, arthritis, infection and tumours as a cause for pain.
For mild to moderate hip pain, rest the area that hurts. Try to avoid activities that are painful or aggravate the pain. Apply ice to the painful area. If the area isn’t swollen, you may apply heat with a heating pad or hot towels. Avoid pain medication as far as possible. It can mask pain messages and allow physical activity that would unduly stress and possibly injure the joint.
As the pain begins to resolve, exercise (mostly stretching and rotation) should be gradually introduced. Swimming, because it stretches the muscles and builds good muscle tone, is recommended after the pain goes away. Cycling or walking can be done gradually.
A walking stick, used on the opposite side of the painful hip, greatly improves the bio-mechanics of that joint, and significantly decreases the pain.
If pain relief is absolutely necessary, anti-inflammatories such as acetaminophen, aspirin, ibuprofen or naproxen can be taken. The maximum recommended dose should reduce the pain, but do not exceed this dosage. Take anti-inflammatory medication only as prescribed by your doctor.
Surgery is recommended when pain and loss of function become severe, medications are no longer effective, and the joint space is severely damaged by arthritis. Of the different procedures available, total hip replacement is almost always successful in relieving pain and improving mobility. It involves replacing the head of the femur and the socket of the pelvis with artificial joints in a surgical procedure under anaesthetic in a hospital.
You will receive an extensive evaluation of your hip to determine if you are a candidate for hip replacement surgery. Evaluation will include assessment of the degree of disability and impact on your lifestyle, pre-existing medical conditions, and an evaluation of heart and lung function.
Total joint replacement is not generally recommended when the following factors are present:
- Poor general health and may not tolerate anaesthesia well
- Severe heart disease, narrowed blood vessels, and poor blood circulation in the limbs
- Severe nerve disease
- An active infection
- Severe overweight
- Young, very active patients.
Cemented total hip replacements are usually indicated for patients over 60 and those with compromised health or poor bone quality and density. Total hip replacements are locked into the bone with a cementing substance called methyl methacrylate. Cemented joints form an immediate, strong bond to the bone.
Cementless total hip replacements are usually indicated for young or active healthy adults. The current mode of fixation is the use of porous coating. Over time, the bone grows into the prepared surface area of the prosthesis, strengthening the joint.
Rehabilitation depends on whether cement or cementless methods were used to attach the replacement parts. Most people are assisted out of bed on the first day after surgery, and physiotherapy usually commences after two to three days of bed rest. Full weight bearing is allowed four to six weeks after surgery, and a walker or crutches may be used for several weeks afterwards. Total rehabilitation takes at least six months.
Complications from surgery include the usual risks of anaesthesia as well as:
- Deep venous thrombosis (formation of a blood clot) – anticoagulants (medication to prevent blood clots) are often used for several weeks following surgery
- Loosening of the artificial joint parts – this is becoming less common with newer artificial joints
- Infection of the artificial joint – antibiotics may be taken prior to and following surgery to reduce this risk
An artificial hip should last at least 15 years in 90 percent of cases with current technology.
Reviewed by Dr Sirk Loots, orthopaedic surgeon.