Arthritis is caused by different factors depending on its type. The two main types are osteoarthritis and rheumatoid arthritis, which damage joints in distinct ways:
- Osteoarthritis is caused by wear-and-tear damage to the cartilage, which is the hard, slick coating on the ends of bones in joints. This damage can happen over many years or be accelerated by joint injury or infection. The cartilage cushions bones and allows smooth joint movement, but when it deteriorates, bones grind directly on each other, causing pain and restricted motion. Osteoarthritis can also involve changes in bones and deterioration of tissues that connect muscles to bones and hold joints together. It is often related to aging, joint overuse, obesity, previous injuries, genetics, and metabolic diseases.
- Rheumatoid arthritis is an autoimmune disease where the body's immune system mistakenly attacks the lining of the joint capsule (synovial membrane), causing inflammation and swelling. This immune attack gradually damages cartilage and bone within the joint, which can ultimately destroy the joint. The precise trigger for this autoimmune reaction is unknown, but genetic factors, hormones, and smoking are thought to contribute to risk.
Other factors that increase risk of arthritis in general include family history, age, sex (for some types like rheumatoid arthritis and gout), previous joint injury, and obesity. In summary, arthritis is caused by either mechanical wear and tear (osteoarthritis) or by immune system malfunction (rheumatoid arthritis), among other less common causes. Various risk factors such as aging, genetics, injury, and lifestyle also play roles in arthritis development. This explanation synthesizes current medical understanding of arthritis causes from reputable sources like Mayo Clinic, NHS, and Arthritis Foundation.
