Osteoarthritis is caused by degeneration in old age that damages the cartilage, resulting in pain during joint movement due to the friction between the bones beneath the cartilage, as well as restricted mobility and even deformity. Rheumatoid arthritis, on the other hand, is typically caused by joint cartilage damage from rheumatic diseases, leading to the destruction of the cartilage. This disease is due to abnormalities in the immune system causing elevated anti-O and rheumatoid factors, and can be definitively diagnosed through etiological examination, physical examination, or blood tests.