Continuing Medical Education: Synovitis.

Edited By: Gregory C. Gardner, M.D.
Last updated Thursday, February 10, 2005

The differential diagnosis of joint pain

What is the differential diagnosis of synovitis?

When evaluating the patient with joint pain, I find it useful to consider six key concepts during the history and physical examination that help me narrow my differential diagnosis. By narrowing the differential, one can focus the work-up in a more expedient and cost efficient manner.

The six key concepts are:

1. Is the joint pain really an arthritis?
2. Is the condition acute or chronic?
3. Is the problem inflammatory or noninflammatory?
4. What is the pattern of joint involvement?
5. Are there associated systemic features?
6. What are the demographics of the patient that might make one diagnosis more tenable?

What structures around a joint might a person present as joint pain?

There are a variety of structures that can become painful and might be interpreted as an arthritis by patients. Causes of joint pain from outside the joint (structures inside the joint capsule) can be from periarticular structures. The following is a list of structures around a joint that might present to you as joint pain.

Periarticular causes of joint pain

1. Bursitis
2. Faciitis
3. Tendonitis
4. Ligament Injury
5. Epicondylitis
6. Myofacial Pain/Fibromyalgia

There are also a variety of nonarticular abnormalities affecting bone, nerve, or blood vessels that may present as joint pain. Below is a list of such causes.

Nonarticular causes of joint pain

1. Tumors of Bone
2. Radiculopathy
3. Osteomyelitis
4. Neuroma
5. Nerve Entrapment
6. Vasculopathy

Differentiation of these problems from an arthritis requires careful physical examination which should include:

1. Inspection of the joint area for evidence of swelling or redness
2. Passive range of motion of the joint(s) in the area noting pain, reduction of motion, or instability
3. Active range of motion of the joint(s) in the area noting pain that was not there when the joint(s) were passively moved
4. Resisted range of motion of the joint(s) in the area again noting pain
5. Palpation of the joint line(s) and surrounding structures noting tenderness, joint effusion(s), and boney changes.
6. Most soft tissue problems do not hurt with passive motion while most forms of arthritis do.
7. Tendonitis is typically painful with active or resisted motion.
8. A bursitis is usually painful only with palpation.
9. Myofacial pain is also painful to palpation and may be widespread as in fibromyalgia.

What do acute and chronic mean?

How do inflammatory and noninflammatory disorders usually present?

This is a very helpful point in limiting your differential diagnosis. Inflammatory disorders usually present with morning stiffness that lasts longer than 30-40 minutes, stiffness that increases with rest, relief of symptoms with exercise, some degree of swelling, and a synovial fluid WBC that is above 2000/mm3. Most of the 2000 cells should also be PMNs.

Noninflammatory disorders usually present with only limited morning stiffness (< 15 minutes), pain with use, relief of pain with rest, swelling may or may not be present, and synovial fluid WBC is typically less than 2000/mm3.

An initial determination of the character of the synovial fluid at the bed side can be made by looking at the fluid in a glass tube against newsprint. The print can still be read through noninflammatory fluid while inflammatory fluid will obscure the print. The intensity of the synovial inflammation is only relatively helpful in the differential diagnosis. Below is a chart of synovial fluid differentiated by cell count. An important point to remember is that an infected joint may not have septic range WBC. If you at all suspect infection send the fluid for gram stain and culture.

Table 1. Synovial fluid analysis

One other type of presentation in this regard is worthy of note. Fibromyalgia typically presents with marked AM stiffness, pain with use and pain and stiffness at night so that it is not clearly inflammatory or noninflammatory.

Surgery for arthritis at the University of Washington

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