Osteoarthritis is the most common diagnosis for patients having total hip replacement. It is also the most common type of arthritis. The vast majority of all patients, men and women, undergoing hip replacement have osteoarthritis. Osteoarthritis is arthritis due to age, repetitive activity, or simple everyday wear and tear. It affects only one joint or a few joints in the body at one time. It is not a systemic process like rheumatoid arthritis. It affects only joints, not other organs in the body. More than 30 million people in the United States are estimated to have osteoarthritis. Symptoms may develop at any time, usually after age 40 years, and the incidence increases with age. It is more common in women.
As the population becomes older more people will develop the disease. No one knows what triggers the onset of osteoarthritis. Besides age and overuse, other factors include being overweight, joint laxity, joint deformity, and abnormal articular cartilage. Long-term high impact activities such as sports can also cause damage to the joint surfaces. The hips, knees, hands, neck, and lower back are the areas most affected by osteoarthritis. It is estimated that by age 65 half of the population has x-ray changes of osteoarthritis in at least one joint. A smaller percentage, however, are actually symptomatic. Symptoms do not always correlate directly with the amount of damage seen on x-ray. You may have severe pain even though an x-ray shows only mild damage to the joint. The main cause of osteoarthritis is breakdown of the joint surface, the articular cartilage.
As the body gets older the cartilage loses its elasticity. It can no longer absorb shock and compressive forces as it once did. It loses the ability to repair itself. When this happens, the joint surface starts to collapse. The underlying bone called subchondral bone reacts by becoming hard or sclerotic. It has a dense or thick white look on x-ray. Bone cysts called subchondral cysts may form in this location. The bone becomes deformed and forms prominences called spurs or osteophytes at the edges of the joint. When the joint cartilage has completely worn away an x-ray will show bone on bone. One bone in the joint can be seen rubbing up against another with no joint space left in between.Pain is the main symptom of an arthritic joint. Stiff-ness, loss of motion, and weakness develop as the disease gets worse. The progress of the disease varies among individuals and even from joint to joint in the same person. Some people may go along for years with the same level of pain and no x-ray changes.
Others have complete destruction of a joint and need surgery within a few short months. Surgery is indicated when you can no longer tolerate the pain and limitation caused by an arthritic joint. In the hip, total hip replacement or arthroplasty is the procedure most often performed for osteoarthritis. Other procedures such as resurfacing, fusion, osteotomy, and arthroscopy will be discussed later in this book. Osteoarthritis is not osteoporosis. Osteoporosis is thinning of the bones in your body. Like osteoarthritis it comes on as the body ages. Unlike osteoarthritis it does not directly involve joints. You can have weak thin bone and still have normal joints. Osteoporosis can predispose to fractures but it is not painful. It is completely different from osteoarthritis.