Activities of daily living, such as climbing stairs or opening jars, often become more difficult as the joints become more affected by the disorder.

Osteoarthritis typically occurs in one or two joints at first, most frequently targeting weight-bearing joints that include:

The pain of osteoarthritis often manifests as a deep ache within or near the affected joint, coupled with a limitation of motion. In OA, most people typically experience joint pain that worsens during the course of the day, whereas others report the greatest pain in the morning (which is related to the symptom of stiffness after activity)

Osteoarthritic pain primarily is caused by joint damage.

Other painful sensations, such as rubbing or grating within the joint, may be felt when a person performs specific activities such as:

As cartilage wears away on the ends of the bones and cushioning is lost, the intensity of pain may increase. Pain may become quite severe if the cartilage has completely deteriorated and the joint becomes unstable.

Sometimes osteoarthritis can cause referred pain - that is, pain that is not experienced directly in the damaged joint, but is felt in other regions instead. For example:

Osteoarthritic pain, like other pain, may worsen after stressful life events, such as the loss of a loved one or separation from a spouse.

Stiffness After Inactivity

After periods of inactivity (for example, sleeping or prolonged sitting), a person may experience considerable stiffness in the osteoarthritic joint. Stiffness usually lasts for about 30 minutes or less and is improved by mild activity that 'warms up' the joint.

Progressive breakdown of cartilage may lead to the formation of enlarged bony growths or "spurs" on the bone ends. Such growths increase the appearance of swelling and knobbiness as they continue the cycle of irritation and swelling.

Once the synovial membrane (smooth tissue that surrounds the joint) becomes irritated by the erosion of cartilage, it may produce an excessive amount of fluid that can collect within the joint and lead to continual or occasional swelling.

Osteoarthritis usually doesn't cause any prominent inflammation (a protective response in which tissue may become red, warm, and tender) in response to injury. This distinguishes it from rheumatoid arthritis, which is associated with considerable joint inflammation. Occasionally people with osteoarthritis experience mild inflammation, although the exact cause of this response remains unknown.