A diagnosis of OA is usually made based on a patient's history of symptoms and a physical exam. These can be augmented by X-rays and certain laboratory tests, which most often are used to exclude the possibility of other diseases. After a diagnosis is made, doctors often ask a series of questions about pain and ability to perform daily activities to assess the seriousness of the disease.
Doctors who perform these exams can be general practitioners. But specialists in arthritis, known as rheumatologists, and specialists in joint surgery, or orthopedists, have the greatest expertise in diagnosis and treatment of OA.
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The medical history and physical exam
Your doctor will ask questions designed to identify the symptoms of OA and to distinguish it from other diseases:
- What joints are involved? OA often affects a joint or joints on only one side of the body, whereas diseases such as rheumatoid arthritis typically affect many more joints on both sides.
- Does any sort of activity provide pain relief? Rest usually relieves OA pain, while activity can lessen stiffness and pain from other kinds of arthritis.
- Have the joints been red or swollen? Significant redness over the joint is not typical for OA but suggests other forms of arthritis. Swelling can be seen in all forms of arthritis.
- Has the joint been injured in the past?
Doctors will also conduct a physical exam, looking at and touching all the joints of the feet, legs, spine, arms, and hands to see how many of them are affected, and moving them to see if motion is impaired.
X-rays and lab tests
An X-ray of a joint that is affected by OA can show narrowing of the joint space. Other abnormalities include "osteophytes," bony growths at the joint that look like little bumps. However, X-rays are not conclusive for diagnosis, because a lot of people experience the pain of OA before changes become apparent. Conversely, an X-ray might show physical changes associated with OA in people who do not report pain or other symptoms.
A test called joint aspiration or arthrocentesis can be used to rule out other illnesses. Under a local anesthetic, a doctor inserts a fine needle into the joint and withdraws a small amount of joint fluid. This fluid can be examined for bacteria or signs of infectious arthritis, inflammation of a joint caused by an infection. It can also be examined for crystals of uric acid, which indicate yet another form of arthritis known as gout.
Similarly, blood tests don't indicate OA but can be used to rule out rheumatoid arthritis. A person with rheumatoid arthritis often has substances in the blood that indicate a systemwide inflammation, while a person with OA does not.
Measurement scales for OA
Once OA has been diagnosed, doctors need to assess the severity of the disease. They often do this by asking a series of questions, or asking patients to fill out questionnaires, about:
Pain: Patients are asked to rate their pain on a scale of 1 to 10 or 1 to 5, where the lowest number indicates "no pain" and the highest indicates "excruciating."
Movement: Patients rate how easy or how difficult it is to move a limb or a joint, and to indicate how far they can move the joint. Sometimes this, too, is measured on a scale of numbers. Patients also can be asked to look at a simple diagram of the body and mark the areas they think are affected.
Function: Patients answer questions about such daily activities as walking, cooking, sitting, playing with their children, and sleeping, indicating how severely they are impaired.
Patients filling out a survey might, for example, rate themselves on a five-point scale in several categories, after which scores are converted to a 0 to 100 scale on which 100 represents the best results. Taken at intervals, such measurements can also give physicians a sense of how well treatments are working.
Last reviewed on 7/21/2009
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