The warning signs of OA include:

• Pain or stiffness in a joint, usually the hip, knee, foot, spine, or fingers.
• Pain that is aggravated by activity and relieved by rest.
• Swelling that may include the area around a joint.
• Symptoms that last longer than two weeks.
• Grating or crunching sound of bones rubbing together when the joint is moved.
• Limited mobility in the affected joint.

If you experience several of these symptoms, see your doctor to find out if you have OA.

The doctor will perform a physical examination including a thorough check of the joint or joints that are causing pain. He or she will be looking for signs that might indicate OA including bumps, enlargement of the bones, restricted motion, fluid build up, weakened muscles, and joint instability. The doctor will also ask you questions about your pain to get a better idea of what is causing it. If necessary, he or she may also recommend tests to help diagnose OA. The most common is X-rays, which show the bones that make up a joint and the space between them (see picture above).  If this space is narrower than usual, it is an indication that the cartilage normally found in between the bones is breaking down (cartilage does not show up in X-rays). X-rays can also show bone spurs around a joint if they are present. Magnetic resonance imaging (MRI) may also be used. This imaging technique shows the soft tissue structures of the joint (including cartilage) in high detail.

The doctor may also recommend tests to help rule out other possible causes of your pain including:

• Blood tests, which can help indicate other causes of joint pain such as infections or rheumatoid arthritis.
• Joint fluid analysis (joint aspiration), which involves taking a small sample of fluid that is normally found inside joints. This can determine if your pain is caused by a condition called gout or a joint infection.
• Arthroscopy, which uses a small camera attached to a wire to see inside the joint. This can help determine if you have an injury to the structures inside the joint that may be causing your pain.