The causes of arthritis are numerous — and some of them are still unknown. Scientists say that the development of joint pain, joint stiffness, and joint swelling can be traced to several contributing factors, including the following:
- Heredity:Scientists have discovered that the genetic marker HLA-DR4 is linked to rheumatoid arthritis; so, if you happen to have this gene, you're more likely to develop the disease. For example, ankylosing spondylitis is linked to the genetic marker HLA-B27, and although having this gene doesn't mean that you will absolutely get this form of arthritis, you can if conditions are right.
- Age: It's just a fact of life that the older you get, the more likely you are to develop arthritis, especially osteoarthritis. Like the tires on your car, cartilage can wear down over time, becoming thin, cracked, or even wearing through. Bones may also break down with age, bringing on joint pain and dysfunction.
- Overuse of a joint: What do ballerinas, baseball pitchers, and tennis players all have in common? A great chance that they'll develop arthritis due to the tremendous repetitive strain they put on their joints. The dancers, who go from flat foot to pointe hundreds of times during a practice session, eventually end up with painful, arthritic ankles. Baseball pitchers, throwing fastballs at speeds of more than 100 mph, regularly develop arthritis of the shoulder and/or elbow. Moreover, you don't need to be a tennis pro to develop tennis elbow, a form of tendonitis that has sidelined many a player.
- Injury: Sustaining injury to a joint (from a household mishap, a car accident, playing sports, or doing anything else) increases the odds that you can develop arthritis in that joint.
- Infection: Some forms of arthritis are the result of bacteria, viruses, or fungi that can either cause the disease or trigger it in susceptible people. Lyme disease comes from bacteria transmitted by the bite of a tick. Rheumatoid arthritis may come from a virus that triggers it in people with a certain genetic marker. Infectious arthritis can arise following surgery, trauma, a needle inserted into the joint, bone infection, or an infection that's traveled from another area of the body.
- Tumor necrosis factor: TNF is a substance the body produces that causes inflammation and may play a part in initiating or maintaining rheumatoid arthritis. Although scientists are unsure exactly what triggers rheumatoid arthritis, they have found that drugs that counteract the effects of TNF, called TNF antagonists, are often helpful in managing the symptoms of this disease.