What does "osteoarthritis" mean and how is it different from rheumatoid arthritis?

Osteoarthritis is a degenerative joint disease where cartilage breaks down over time, from osteo meaning bone, arthr meaning joint, and itis meaning inflammation. It is the most common form of arthritis, affecting weight-bearing joints like knees and hips, and worsens with age and use. Rheumatoid arthritis is an autoimmune disease where the immune system attacks the synovial membrane lining the joints, from rheumato meaning watery flow and arthr meaning joint. ---