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|How Is Osteoarthritis Diagnosed?
There is no one specific test for osteoarthritis. Instead, a diagnosis is based on a comprehensive evaluation of the patient. According to guidelines recommended by the American College of Rheumatology, a clinical diagnosis of osteoarthritis should only be given based on physical examination, a patient's medical history and X-ray result.
While osteoarthritis is usually visible with an X-ray, in the early stages of the disease it may be missed. A physical examination, particularly if the hand is affected can be more accurate. Before sending you for tests, your doctor will perform a medical examination. He will check for:
• Tenderness along the joint line.
• A crackling sound (crepitus) when the joint is moved.
• If the bone is larger than normal.
• Any bony lumps near the joint (such as Heberden's or Bouchard's nodes on the finger).
• If normal movement is restricted or painful.
• Instability of the joint, does the joint give way under you?
• Altered walk (gait) if the knee or hip is affected.
See: symptoms of osteoarthritis for more details.
In taking your medical history your doctor will want to know:
• When does pain occur and is it linked to certain activities.
• How pain affects your home, work or recreational life.
• How well you are coping with the pain.
• Signs of avoidant posturing - are you standing or walking in certain ways to avoid triggering pain.
• Signs of depression such as irritability, weight loss and concentration problems.
Osteoarthritis which has developed beyond the early stages is usually visible on X-ray. The x-ray will typically reveal:
• Cartilage loss, the space between the bones and joint is narrower than normal.
• Bones are thicker (denser) than normal.
• Small lumps of bone are growing off the main bones (bone spurs). There may also be fluid filled cysts or signs of bone erosion.
An MRI scan is not generally ordered unless the doctor suspects another cause of pain. Thermal imaging may be useful in differentiating between osteoarthritis and rheumatoid arthritis, but it is not considered a standard test.
Sometimes other types of arthritis, such as gout or rheumatoid arthritis can be present with osteoarthritis. The following blood tests may be recommended to rule out other conditions:
Rheumatoid factor (RF): The presence of this protein indicates a likelihood of rheumatoid arthritis (RA) being present. However, it can also be present in 5 to 10 percent of healthy women. It is also frequently absent in elderly-onset RA (where the disease first appears after the age of 60). Still, it is present in 80 percent of those with RA.
Anti-citrullinated protein antibody (ACPA): Newer test, considered even more accurate than RF in diagnosising RA.
Erythrocyte sedimentation rate (ESR, or sed rate): Often elevated in those with RA or lupus.
Raised uric acid levels in the blood may indicate gout. Uric acid crystals can form in the joints (particularly the joint of the big toe). This is a painful condition called gout.
Synovial Fluid Test
Also called: arthrocentesis or joint aspiration.
If your doctor is still uncertain about the diagnosis, or an infection is suspected, he may attempt to withdraw a sample of synovial fluid from around the joint with a needle. In a healthy joint, there will not be enough fluid to withdraw. If fluid does come out, problems are likely. The fluid will be tested for factors that will either confirm or rule out osteoarthritis:
• High white blood cell count is a sign of infection, indicating RA, gout or pseudogout (calcium crystals gathering in the joints).
• Cartilage cells in the fluid are a sign of osteoarthritis.
• Uric acid crystals are a sign of gout.
Ruling Out Other Conditions
Lots of conditions can cause aching joints and pain (see, why do I ache all over?). Osteoarthritis can usually be distinguished by 3 factors:
1. It tends to occur in older people and is located in one or a few joints.
2. The joints are not as inflamed as in other types of arthritis.
3. Symptoms occur gradually, over a number of years.
The following is a list of other conditions which are sometimes mistaken for osteoarthritis, or which may occur alongside it:
Osteoarthritis can sometimes be confused with mild forms of RA, particularly if osteoarthritis affects more than one joint. However, RA usually occurs earlier in life, striking a person in their 30s or 40s. RA tends to affects many joints of the body at once, often on both sides of the body. RA patients have morning stiffness that can last several hours, whereas osteoarthritis stiffness usually clears within half an hour. While osteoarthritis can very occasionally cause red or swollen joints, this appearance is much more typical of RA and other inflammatory types of arthritis. Blood tests will help your doctor differentiate between the two. It is important to diagnose the correct type of arthritis because treatments differ. See treatment for rheumatoid arthritis and treatment for osteoarthritis for details.
Chondrocalcinosis (pseudogout syndrome)
This is a disease that causes calcium crystals known as CPPD (calcium pyrophosphate dihydrate) to accumulate in the joints. It is also called pseudogout or pseudo-osteoarthritis (the latter when it affects the knee). It may be present on its own, or it can accompany osteoarthritis, making the condition more painful. Pseudogout is more likely to damage joints in the shoulders, wrists or elbows, areas not usually affected by osteoarthritis. This makes the diagnosis easier.
Also called neuropathic joint, this condition strikes when an underlying disease causes nerve damage in the joint so that it swells and bleeds. Charcot joint leads to loss of sensation in the area. It is usually easily diagnosed because no-one with sensation in the area could tolerate the sort of pain associated with the joint damage it causes. It is usually a complication of diabetes.