Osteoarthritis is caused by aging and mechanical wear and tear on articular cartilage, leading to cartilage thinning, bone thickening, and joint swelling. Rheumatoid arthritis is an autoimmune disease in which the immune system attacks the body's own tissues, causing inflammation of the joint capsule and synovial membrane and eventual cartilage damage.

Osteoarthritis (OA) and rheumatoid arthritis (RA) differ in their underlying cause and pathophysiology. OA is associated with aging and wear and tear of the articular cartilage at a synovial joint. Over time the cartilage becomes thinner, placing more pressure on the bones. The joint may respond by increasing synovial fluid production, which can cause swelling, and the bone under the damaged cartilage thickens, making the articular surface rough or bumpy. These changes lead to pain and inflammation with joint movement. RA, in contrast, is an autoimmune disease. The immune system attacks the body's own tissues, and the joint capsule and synovial membrane become inflamed. As RA progresses, the articular cartilage is severely damaged, causing joint deformation, loss of movement, and potentially severe disability.

Key points

OA stems from aging and mechanical wear and tear on articular cartilage.
RA stems from an autoimmune attack on the body's own tissues.
In OA, cartilage gradually thins and bone beneath becomes thickened and rough.
In RA, the joint capsule and synovial membrane become inflamed before cartilage is severely damaged.
Both cause joint pain and inflammation, but their mechanisms of damage differ.

How does osteoarthritis differ from rheumatoid arthritis in terms of underlying cause and pathophysiology?

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