Osteoarthritis is a common degenerative disorder of the articular cartilage associated with hypertrophic bone changes. Risk factors include genetics, female sex, past trauma, advancing age, and obesity. The diagnosis is based on a history of joint pain worsened by movement, which can lead to disability in activities of daily living. Plain radiography may help in the diagnosis, but laboratory testing usually does not. Pharmacologic treatment should begin with acetaminophen and step up to nonsteroidal anti-inflammatory drugs. Exercise is a useful adjunct to treatment and has been shown to reduce pain and disability. The supplements glucosamine and chondroitin can be used for moderate to severe osteoarthritis when taken in combination. Corticosteroid injections provide inexpensive, short-term (four to eight weeks) relief of osteoarthritic flare-ups of the knee, whereas hyaluronic acid injections are more expensive but can maintain symptom improvement for longer periods. Total joint replacement of the hip, knee, or shoulder is recommended for patients with chronic pain and disability despite maximal medical therapy.