In a previous article ("What is osteoarthritis"), I discussed how osteoarthritis develops.

In this article, I'll talk about how the diagnosis is made.

The diagnosis of osteoarthritis can usually be made clinically. The history and physical examination are usually enough. However, the diagnosis is often confirmed by using x-rays as well as laboratory tests.

The primary goal is to differentiate osteoarthritis from other forms of arthritis. The most common other form of arthritis that can be confused with osteoarthritis is rheumatoid arthritis.

As mentioned in a previous article, osteoarthritis affects primarily weight-bearing joints such as the neck, low back, hips, knees, feet, and the base of the thumb.

Rheumatoid arthritis affects small joints such as the risks and the hands. In the hands the metacarpal phalangeal joints-the knuckles-and the PIP joints-the middle row of finger joints, are most commonly affected.

In addition, the feet and ankles are often affected early as well.

As rheumatoid arthritis progresses, other large joints may become involved. These include the shoulders, elbows, hips, and knees.

Unlike osteoarthritis, rheumatoid arthritis is associated with significant morning stiffness. While patients with osteoarthritis may complain of morning stiffness lasting 15 minutes to half an hour, patients with rheumatoid arthritis may have morning stiffness lasting at least an hour or longer.

In addition, x-ray findings of room for rheumatoid arthritis are very different from the x-ray findings seen with osteoarthritis.

Laboratory findings may help differentiate rheumatoid arthritis from osteoarthritis are the presence of a positive rheumatoid factor, positive anti--CCP, as well as elevated erythrocyte sedimentation rate.

In addition, in patients who have a significant effusion-fluid within the joint-that fluid will have a markedly elevated white blood cell count in rheumatoid arthritis.

Other types of arthritis such as calcium pyrophosphate arthropathy may also look like osteoarthritis.

Spondyloarthies inflammatory forms of arthritis that may affect the spine, can also affect other joints as well, making the distinction from osteoarthritis sometimes difficult.

Following history and physical examination, laboratory testing should be undertaken.

Bloodwork including complete blood count, erythrocyte sedimentation rate, serum chemistries, thyroid function tests, serum uric acid, rheumatoid factor, and anti-CCP antibodies, should be obtained.

X-rays of the most affect it areas may also be helpful. In patients where rheumatoid arthritis is suspected, early magnetic resonance imaging scans may be helpful. Magnetic resonance imaging can sometimes diagnose very early rheumatoid arthritis.

Patients who have effusions in their joints may need to undergo arthrocentesis. Joint fluid examination may be helpful. In particular, patients who have crystal associated arthritis such as calcium pyrophosphate disease or gout may have their disease diagnosed through this route.

In rare instances, the patient may need to undergo synovial biopsy in order to make the diagnosis.

It is not uncommon for patients to have more than one kind of arthritis. Therefore, the workup should be performed with that in mind.

Finally, some patients may also have concomitant fibromyalgia, a soft tissue form of arthritis that can make diagnosis difficult.

Arthritis treatment will be discussed in a future article.