Arthritis of the hip is any deviation from the normal smoothness of the surfaces that make up the hip joint. The term arthritis is a bit of a loose description that denotes rough, worn and painful joint surfaces. There are many different causes of arthritis of the hip, and the arthritis can manifest itself in varying degrees of severity.
Aging
As we get older, our joints begin to wear out, losing the natural supple texture of the joint cartilage, and the wearing down of these surfaces to the point that raw underlying bone can be exposed. As these surfaces degenerate and deteriorate, the joint becomes increasingly stiff and painful. The garden-variety term for this type of aging-related arthritis is osteoarthritis.
Infection
Any time an infection invades a joint space, there is considerable risk it will damage or even destroy the joint surfaces. Pus under pressure in a joint is very destructive and a cause for urgent treatment. The term for arthritic conditions arising from infection is septic arthritis. This arthritis type is more frequently found in children than adults. It can result from infections caused by such things as seeding, which is the inoculation of the body with micro-organisms from elsewhere in the body. One example is a hip infection caused by dental cleaning, perhaps in a person whose immune system is depressed. Another example is seen in the chronic kidney patient who undergoes frequent, if not daily, dialysis involving multiple needle punctures in the arms. People whose immune systems are chronically compromised are at higher risk of such infections and should take care to minimize infection risk.
Trauma
Often, direct trauma to a hip joint can ultimately lead to its degeneration, thus causing arthritis. One of the most common examples arises from prior hip dislocations, resulting in compromise of the blood supply to the hip joint. This can ultimately lead to a condition known as avascular necrosis, or death of the bone. Necrosis typically occurs in the femoral head, or ball, of the hip; and the loss of blood supply causes not only the bone but also the cartilage surfaces to degenerate.
Systemic Disease
Certain systemic diseases can affect any joint, the hip included. An example of a systemic disease that can wreak havoc on joints is rheumatoid arthritis. In this auto-immune disease, the body literally attacks itself. This is more a disease of the joint linings than of the joint surfaces themselves. The membranous lining, called the synovium, becomes so inflamed and swollen it invades the joint from the outer margins inward, ultimately destroying the cartilage and causing the arthritis.
