Osteoarthritis is a localized, degenerative condition with gradual cartilage destruction, incomplete repair, new bone formation, and bony spurs, typically affecting the hands, knees, spine, and hips. Rheumatoid arthritis is a chronic, progressive, systemic autoimmune disorder in which the synovial lining becomes inflamed and congested with lymphocytes, leading to erosion of cartilage and bone, and it particularly affects the hands, fingers, and shoulders, often starting in the peripheral joints of the hands and feet.

Key points

OA is localized and degenerative; RA is autoimmune, chronic, progressive, and systemic.
In OA, joint cartilage is gradually destroyed with incomplete repair and formation of new bone and bony spurs.
In RA, the synovial lining of the joint capsule becomes inflamed and congested with lymphocytes, leading to cartilage and bone erosion.
OA most often affects the hands, knees, spine, and hips.
RA particularly affects the hands, fingers, and shoulders, and as it progresses other joints become affected.
RA can also cause extra-articular features and systemic symptoms, whereas OA is mainly localized to the affected joints.

What are the main differences between osteoarthritis and rheumatoid arthritis in terms of pathology and affected joints?