Virtually any form of arthritis can affect the knee, and cause pain and swelling. These include:

Osteoarthritis. The most common form of arthritis, osteoarthritis is a chronic condition characterized by the breakdown of the cartilage that cushions the ends of the bones where they meet to form joints. The breakdown of cartilage causes the bones to rub against each other, causing stiffness, pain and loss of movement in the joint. The knee is one of the joints most commonly affected by osteoarthritis.

Read about osteoarthritis treatment, pain management and more.

Experts answer your questions about osteoarthritis.

Learn how being overweight can increase your risk of osteoarthritis. 

Read how researchers use X-rays to predict the development of knee osteoarthritis.

Rheumatoid arthritis. Rheumatoid arthritis is a chronic inflammatory disease of the joints which occurs when body’s immune system – which normally protects us from infection – mistakenly attacks the synovium, the thin membrane that lines the joints. The result can be joint damage, pain, swelling, inflammation, loss of function and disability. In addition to the knees, rheumatoid arthritis, commonly affects the hands, wrists, feet, elbows and ankles.

Learn more about rheumatoid arthritis, including treatment, pain issues and how staying active helps.

Read about rheumatoid arthritis news and research.

Juvenile arthritis. Juvenile arthritis is the term used to describe arthritis when it begins at age 16 or before. There are several different types of juvenile arthritis, including juvenile rheumatoid arthritis (JRA) and juvenile idiopathic arthritis (JIA). Many can cause pain and swelling of the knee.

Learn more about the types of juvenile arthritis.

Read more about coping with juvenile arthritis.

Gout. Gout is a form of arthritis that occurs when excess uric acid, a bodily waste product circulating in the bloodstream, is deposited as needle-shaped monosodium urate crystals in tissues of the body, including the joints. For many people, the first symptom of gout is excruciating pain and swelling in the big toe – often following a trauma, such as an illness or injury. Subsequent attacks may occur off and on in other joints, primarily those of the foot and knee, before becoming chronic.

Read more about gout, including risk factors, medications and diet.