Causes
There is no single cause of all types of arthritis. The cause or causes vary according to the type or form of arthritis.
Possible causes may include:
- injury, leading to degenerative arthritis
- abnormal metabolism, leading to gout and pseudogout
- inheritance, such as in osteoarthritis
- infections, such as in the arthritis of Lyme disease
- immune system dysfunction, such as in RA and SLE
Most types of arthritis are linked to a combination of factors, but some have no obvious cause and appear to be unpredictable in their emergence.
Some people may be genetically more likely to develop certain arthritic conditions. Additional factors, such as previous injury, infection, smoking, and physically demanding occupations, can interact with genes to further increase the risk of arthritis.
Diet and nutrition can play a role in managing arthritis and the risk of arthritis, although specific foods, food sensitivities, or intolerances are not known to cause arthritis.
Foods that increase inflammation, particularly animal-derived foods and diets high in refined sugar, can make symptoms worse, as can eating foods that provoke an immune system response.
Gout is one type of arthritis that is closely linked to diet, as it is caused by elevated levels of uric acid which can be a result of a diet high in purines.
Diets that contain high-purine foods, such as seafood, red wine, and meats, can trigger a gout flare-up. Vegetables and other plant foods that contain high levels of purines do not appear to exacerbate gout symptoms, however.
Risk factors for arthritis
Certain risk factors have been associated with arthritis. Some of these are modifiable while others are not.
Non-modifiable arthritis risk factors:
- Age: the risk of developing most types of arthritis increases with age.
- Sex: most types of arthritis are more common in females, and 60 percent of all people with arthritis are female. Gout is more common in males than females.
- Genetic factors: specific genes are associated with a higher risk of certain types of arthritis, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and ankylosing spondylitis.
Modifiable arthritis risk factors:
- Overweight and obesity: excess weight can contribute to both the onset and progression of knee osteoarthritis.
- Joint injuries: damage to a joint can contribute to the development of osteoarthritis in that joint.
- Infection: many microbial agents can infect joints and trigger the development of various forms of arthritis.
- Occupation: certain occupations that involve repetitive knee bending and squatting are associated with osteoarthritis of the knee.
Comorbidities
More than half of adults in the U.S. with arthritis report high blood pressure. High blood pressure is associated with heart disease, the most common comorbidity among adults with arthritis.
Around 1 in 5 adults in the U.S. who have arthritis are smokers. Smoking is associated with chronic respiratory conditions, the second most common comorbidity among adults with arthritis.
Types
There are around 200 types of arthritis or musculoskeletal conditions. These are split into seven main groups:
- Inflammatory arthritis
- Degenerative or mechanical arthritis
- Soft tissue musculoskeletal pain
- Back pain
- Connective tissue disease
- Infectious arthritis
- Metabolic arthritis.