Your doctor makes the diagnosis of OA on the basis of your history and the results of your physical examination. People with OA usually complain of pain, stiffness, or joint swelling, or some combination of these symptoms. During your physical exam, your doctor will pay special attention to your joints. He or she will check for swelling, tenderness, redness, joint effusions (fluid inside the joint), and your ability to flex and extend the affected joints.
Your physician will also evaluate the distribution of affected joints. The pattern of distribution of inflamed joints varies according to the type of arthritis and can be an important clue in making a diagnosis of OA. For example, OA typically affects the middle knuckle joints, the distal knuckle joints (next to the fingernails), and the base of the thumb. The hips, knees, feet (especially the big toe), neck, and low back are other common sites for OA. In comparison, rheumatoid arthritis (RA) typically affects the wrists and the first knuckle joints of the hands; these joints are seldom affected by OA. Your doctor should look for other physical findings associated with OA, such as muscle wasting and weakness.
The diagnosis of osteoarthritis is made on the basis of your history and the results of your physical examination. There is no particular test whose results can be used to make a definitive diagnosis of OA.
There is no particular test whose results can be used to make a definitive diagnosis of OA, so special tests such as blood tests and x-rays are usually not needed when this condition is suspected. Occasionally, your doctor may order one or more of these tests if he or she needs to exclude other arthritic conditions. Blood tests and radiographs may also be helpful for monitoring for side effects of medications or to help determine the extent of joint damage when considering surgical treatment.