The hip joint is a ball-and-socket joint: the ball is the head of your thighbone called the femur, and the socket is an area of the pelvis called the acetabulum. The hip joint is the articulation of the pelvis with the femur. The hip’s unique anatomy enables it to be both extremely strong and amazingly flexible, so it can bear weight and allow for a wide range of movement.
Also known as the acetabulofemoral joint, the hip joint is comprised of these basic components:
- Hip bones, including the femur and pelvic bones;
- Hip articular cartilage that decreases friction between the bones and allows for a smooth gliding motion;
- Hip muscles that both support the joint and enable movement;
- Hip ligaments and tendons, tough, fibrous tissues that bind bones to bones and muscles to bones; and
- Synovial membrane and fluid, which encapsulates the hip joint and lubricates it, respectively.
Hip problems occur when any one of these components starts to degenerate or is in some way compromised or irritated.
Osteoarthritis is a degenerative type of arthritis that occurs most often in people 50 years of age and older, though it may occur in younger people, too.
In osteoarthritis, the cartilage in the hip joint gradually wears away over time. As the cartilage wears away, it becomes rough and frayed, and the joint space between the bones decreases. This can result in bone rubbing on bone. To make up for the lost cartilage, the damaged bones may start to grow outward and form bone spurs (osteophytes).
Osteoarthritis develops slowly and the pain it causes worsens over time.
Bursae are sacs of liquid found between tissues such as bone, muscles, and tendons. They ease the friction from these tissues rubbing together. When bursae get inflamed, they can cause pain. Inflammation of bursae is usually due to repetitive activities that overwork or irritate the hip joint.
Tendons are the thick bands of tissue that attach bones to muscles. Tendinitis is inflammation or irritation of the tendons. It’s usually caused by repetitive stress from overuse.
Muscle or tendon strain
Repeated activities can put strain on the muscles, tendons, and ligaments that support the hips. When they become inflamed due to overuse, they can cause pain and prevent the hip from working normally.
Hip labral tear
This is a rip in the ring of cartilage (called the labrum) that follows the outside rim of the socket of your hip joint. Along with cushioning your hip joint, your labrum acts like a rubber seal or gasket to help hold the ball at the top of your thighbone securely within your hip socket. Athletes and people who perform repetitive twisting movements are at higher risk of developing this problem.
Snapping hip is a condition in which you feel a snapping sensation or hear a popping sound in your hip when you walk, get up from a chair, or swing your leg around.
The snapping sensation occurs when a muscle or tendon (the strong tissue that connects muscle to bone) moves over a bony protrusion in your hip.
Although snapping hip is usually painless and harmless, the sensation can be annoying. In some cases, snapping hip leads to bursitis, a painful swelling of the fluid-filled sacs that cushion the hip joint.
Avascular necrosis (also called osteonecrosis)
This condition happens when blood flow to the hip bone slows and the bone tissue dies. Although it can affect other bones, avascular necrosis most often happens in the hip. It can be caused by a hip fracture or dislocation, or from the long-term use of high-dose steroids (such as prednisone), among other causes
Hip fractures most commonly occur from a fall or from a direct blow to the side of the hip. Some medical conditions such as osteoporosis, cancer, or stress injuries can weaken the bone and make the hip more susceptible to breaking. In severe cases, it is possible for the hip to break with the patient merely standing on the leg and twisting.
A hip fracture almost always requires surgical repair or replacement, followed by months of physical therapy. Taking steps to maintain bone density and avoid falls can help prevent hip fracture
Total Hip Replacement
If your hip has been damaged by arthritis, a fracture, or other conditions, common activities such as walking or getting in and out of a chair may be painful and difficult. Your hip may be stiff, and it may be hard to put on your shoes and socks. You may even feel uncomfortable while resting.
If medications, changes in your everyday activities, and the use of walking supports do not adequately help your symptoms, you may consider hip replacement surgery. Hip replacement surgery is a safe and effective procedure that can relieve your pain, increase motion, and help you get back to enjoying normal, everyday activities.
During surgery, your doctor will remove both the damaged acetabulum and femoral head, and then position new metal, plastic or ceramic joint surfaces to restore the function of your hip and reduce or eliminate pain.
- The damaged femoral head is removed and replaced with a metal stem that is placed into the hollow center of the femur. The femoral stem may be either cemented or “press fit” into the bone.
- A metal or ceramic ball is placed on the upper part of the stem. This ball replaces the damaged femoral head that was removed.
- The damaged cartilage surface of the socket (acetabulum) is removed and replaced with a metal socket. Screws or cement are sometimes used to hold the socket in place.
- A plastic, ceramic, or metal spacer is inserted between the new ball and the socket to allow for a smooth gliding surface.
It is important to understand when deciding whether to have hip replacement surgery what the procedure can and cannot do. Most people who undergo hip replacement surgery experience a dramatic reduction of hip pain and a significant improvement in their ability to perform the common activities of daily living.
With normal use and activity, the material between the head and the socket of every hip replacement implant begins to wear. Excessive activity or being overweight may speed up this normal wear and cause the hip replacement to loosen and become painful. Therefore, most surgeons advise against high-impact activities such as running, jogging, jumping, or other high-impact sports.
Realistic activities following total hip replacement include unlimited walking, swimming, golf, driving, hiking, biking, dancing, and other low-impact sports.
With appropriate activity modification, hip replacements can last for many years.
Total Hip Revision
Although most total hip replacements are very successful, problems can develop over time. These problems may require a revision procedure to replace the original components.
There are different types of revision surgery. In some cases, only some components of the prosthesis need to be revised. In other cases, the whole prosthesis needs to be removed or replaced and the bone around the hip needs to be rebuilt with augments (metal pieces that substitute for missing bone) or bone graft.
The vast majority of patients who undergo revision surgery do experience favorable long-term outcomes. This includes relief from pain, increased stability, and better function. Complete pain relief and restoration of function are not always achievable, however, and some patients may still experience some pain or dysfunction following revision surgery.