Osteoarthritis (OA, also known as degenerative arthritis or degenerative joint disease, and sometimes referred to as "arthrosis" or "osteoarthrosis"), is a condition in which low-grade inflammation results in pain in the joints, caused by wearing of the cartilage that covers and acts as a cushion inside joints. As the bone surfaces become less well protected by cartilage, the patient experiences pain upon weight bearing, including walking and standing. Due to decreased movement because of the pain, regional muscles may atrophy, and ligaments may become more lax. OA is the most common form of arthritis. more...
The word is derived from the Greek word "osteo", meaning "of the bone", "arthro", meaning "joint", and "itis", meaning inflammation, although many sufferers have little or no inflammation.
OA affects nearly 21 million people in the United States, accounting for 25% of visits to primary care physicians, and half of all NSAID (Non-Steroidal Anti-Inflammatory Drugs) prescriptions. It is estimated that 80% of the population will have radiographic evidence of OA by age 65, although only 60% of those will be symptomatic (Green 2001). Treatment is with NSAIDs, local glucocorticoid injections, and in severe cases, with joint replacement surgery. There is no cure for OA, as it is impossible for the cartilage to grow back.
Signs and symptoms
The main symptom is chronic pain, causing loss of mobility and often stiffness. "Pain" is generally described as a sharp ache, or a burning sensation in the associated muscles and tendons. OA can cause a crackling noise (called "crepitus") when the affected joint is moved or touched, and patients may experience muscle spasm and contractions in the tendons. Occasionally, the joints may also be filled with fluid. Humid weather increases the pain in many patients.
OA commonly affects the hand, feet, spine, and the large weight-bearing joints, such as the hips and knees, although in theory, any joint in the body can be affected. Progressive degeneration of cartilage, technically known as synovium (joint lining), in the knees can lead to them curving outwards in a condition known as "bow legged". As OA progresses, the affected joints appear larger, are stiff and painful, and usually feel worse, the more they are used throughout the day, thus distinguishing it from rheumatoid arthritis.
In smaller joints, such as at the fingers, hard bony enlargements, called Heberden's nodes and/or Bouchard's nodes, may form, and though they are not necessarily painful, they do limit the movement of the fingers significantly. OA at the toes leads to the formation of bunions, rendering them red or swollen.
Causes of disease
The crucial factor in the development of OA is the wearing out and eventual disappearance of synovium, and later, all cartilage of the affected joints. OA may be divided into two types:
- Primary OA: This type is caused by ageing. As a person ages, the water content of the cartilage increases, and the protein composition in it degenerates, thus degenerating the cartilage through repetitive use or misuse. Inflammation can also occur, and stimulate new bone outgrowths, called "spurs" (osteophyte), to form around the joints. Sufferers find their every movement so painful and debilitating that it can also affect them emotionally and psychologically.
- Secondary OA: This type is caused by other diseases or conditions such as:
- obesity. Obesity puts added weight on the joints, especially the knees.
- repeated trauma. Certain sports, such as weightlifting, or even football, put undue pressure on the knee joints.
- hormonal disorders
- surgery to the joint structures
- congenital hip luxation (which is genetically determined)
- inflammatory diseases (such as Perthes' disease), and all chronic forms of arthritis (e.g. rheumatoid arthritis and gout). In gout, uric acid crystals cause the cartilage to degenerate at a faster pace.
- People with abnormally-formed joints are more vulnerable to OA, as added stress is specifically placed on the joints whenever they move.
- Ligamentous deterioration or instability may be a factor.
OA often affects multiple members of the same family, suggesting that there is a hereditary basis for this condition. A number of studies have shown that the there is a greater prevalence of the disease between siblings, and especially twins, indicating a hereditary basis. In the population as a whole up to 60% of OA is thought to be as a result of genetic factors.
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