How is osteoarthritis diagnosed?

Blood tests can help eliminate other types of arthritis and other medical problems, while a sample of the joint fluid from the knee can also show typical changes of osteoarthritis.

Usually by the time a person seeks treatment for osteoarthritis, there are changes visible on x-ray of the joint.  There may be a narrowing of the cartilage on the x-ray, but no destruction as with rheumatoid arthritis.

Generally, it is not difficult to tell if a person has osteoarthritis. The signs and symptoms that you describe and your test results will enable your doctor to make a diagnosis. Be aware that no single test can diagnose osteoarthritis.

It is more difficult to determine if the disease is actually the cause of the symptoms. The doctor will try to rule out other disorders, such as joint infection, fracture, injury, gout, bursitis, and other conditions, that may cause the same symptoms as osteoarthritis or make these symptoms worse.

Most likely, your doctor will begin by asking you to describe the pain, stiffness, and joint function (including when and how these symptoms started) and to explain how your symptoms have changed over time. It also is important for the doctor to know how your symptoms are affecting your work and daily life, what other medical conditions you have, and whether you are taking any medications or nutritional supplements.

Your doctor will check your general health, including reflexes and muscle strength and your ability to walk, bend, and carry out daily activities. When examining your joints, your doctor can feel the bony swelling and hear the creaking of the joint. Your doctor will look for tenderness, any thinning of muscles, excess fluid, or instability in the joints. You will be asked to move your limbs as far as you can, to see if your joints restrict movements. Your doctor also will move your limbs to check for any restricted movement.

X rays may be used to confirm that the joint problems are caused by osteoarthritis and not some other form of arthritis. In affected joints, x rays will show how much joint and bone damage has been done. For example, the spaces between the bones affected by osteoarthritis may be narrower than in normal joints because of thinning of the cartilage and extra bone growth such as bone spurs.

There may be a big difference between the severity of osteoarthritis that the x rays show and the degree of pain and disability that you experience. X rays help the doctor make a diagnosis but do not indicate how much the osteoarthritis will bother you. Also, x rays may not show early osteoarthritis damage.

There is no blood test for osteoarthritis. However, blood tests are sometimes done to make sure that your symptoms are not caused by another type of arthritis.

In some cases, the doctor may draw fluid from inside the affected joint, for example, to check for particles that may cause pain.

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General: Once individuals are diagnosed with osteoarthritis, they should visit their healthcare providers regularly, at least once a year. Individuals should stay in close contact with their doctors to ensure that their symptoms are managed and joint damage is monitored.

X-ray: X-rays are often the first test performed if a patient has symptoms of osteoarthritis. If the patient has osteoarthritis, the x-ray images will often show loss of cartilage in the affected joints, narrowing of the space between bones, and bumps called nodules.

Arthrocentesis: A procedure called arthrocentesis may also be performed at a healthcare provider's office. During the procedure, a needle is inserted into the affected joint, and a small sample of fluid is removed. The fluid is then analyzed to rule out other conditions, such as gout or infection. This test may also temporarily relieve some pain and inflammation in the joint.

Arthroscopy: A surgical procedure called arthroscopy may also be performed. During the surgery, a small incision is made into the affected joint. Then a tube called an arthroscope is inserted into the joint. This tube has a small light and camera, which allows the healthcare provider to see the inside of the joint. If abnormalities, including cartilage or ligament damage are seen, the individual is diagnosed with osteoarthritis.

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In most cases, your doctor can tell you if you have osteoarthritis and recommend treatment based on your symptoms and by doing a physical exam. Your doctor may also do some other tests to be sure that the diagnosis is correct or to rule out other conditions that have similar symptoms.

These tests may include:

• A joint fluid study. A sample of the fluid that cushions the joint is removed and sent to the lab to look for the cause of joint pain and swelling.
• X-rays. Pictures of the bones in a joint, such as the hip or knee, are taken to look for cartilage damage.
• An arthroscopy. A thin, lighted tube called an arthroscope is placed inside a small cut made near the joint. The doctor uses the scope to look for problems on the surfaces of the joint and the soft tissues that surround it. This test is not done very often.

Other tests may include a urine test and one or more blood tests, such as:

• Complete blood count (CBC).
• Rheumatoid factor (RF).
• Antinuclear antibody (ANA).
• Sedimentation rate (sed rate).
• C-reactive protein (CRP).
• Chemistry screen.
• Thyroid-stimulating hormone (TSH).
• Ferritin.