Diagnosis
Osteoarthritis is often visible on x-rays. Cartilage loss is indicated by certain images:
- If the normal space between the bones in a joint is narrowed.
- If there is an abnormal increase in bone density.
- If bony projections, cysts, or erosions are evident.
- X-rays can also reveal any cysts that might develop in osteoarthritic joints. If other conditions are suspected or if the diagnosis is uncertain, additional tests will be performed.
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| X-rays are a form of electromagnetic radiation (like light); they are of higher energy, however, and can penetrate the body to form an image on film. Structures that are dense (such as bone) will appear white, air will be black, and other structures will be shades of gray depending on density. X-rays can provide information about obstructions, tumors, and other diseases, especially when coupled with the use of barium and air contrast within the bowel. |
Blood Tests
Blood test results may help diagnose or rule out osteoarthritis. Some examples include the following:
- Elevated levels of rheumatoid factor (specific antibodies in the synovium) and so-called erythrocyte sedimentation rates (ESR or sed rate) indicate rheumatoid arthritis.
- Byproducts of hyaluronic acid, a joint lubricant, may prove to be markers of the lubricant's breakdown and an indicator of osteoarthritis.
- Elevated levels of a factor called C-reactive protein, which is produced by the liver in response to inflammation, are proving to be good predictors of osteoarthritic progression in the knee.
Tests of the Synovial Fluid
If the diagnosis is uncertain or infection is suspected, the physician may attempt to withdraw synovial fluid from the joint using a needle. If the joint is normal, there is not enough fluid to withdraw. If there is, then problems are likely and the fluid is tested for factors that might confirm or rule out osteoarthritis:
- Cartilage cells in the fluid are signs of osteoarthritis.
- A high white blood cell count is a sign of infection.
- High uric acid in the fluid is an indication of gout.
- Other factors may be present that suggest different arthritic conditions, including Lyme disease and rheumatoid arthritis.
- In people with known osteoarthritis, researchers may look for certain factors in synovial fluid (e.g., sulfated glycosaminoglycan, keratin sulfate, and link protein) that can suggest a more or less severe condition.
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