2.1
Arthritis refers to inflammation of a joint, and is a leading cause of pain and disability in the UK. Arthritis can have many causes, the most common of which is osteoarthritis (defined by a loss of cartilage within the joint and related changes in the associated bone). Estimates suggest that up to 8.5 million people in the UK are affected by joint pain that may be attributed to osteoarthritis. The second most common cause is rheumatoid arthritis (an autoimmune inflammatory disease that affects the synovial lining of joints). Around 400,000 people in the UK have rheumatoid arthritis.