9.09 Acute Monarticular Arthritis
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agk's Library of Common Simple Emergencies

Presentation
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The patient complains of one joint which has 
become acutely red, swollen, hot, painful, and 
stiff.

What to do:
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- Ask about previous, similar episodes in this 
    or other joints, as well as trauma, infect- 
    ions, or rashes, and perform a thorough 
    physical examination looking for evidence 
    of the same. Ask for a history of [gout].
- Examine the affected joint, and document the 
    extent of effusion, involvement of adjacent 
    structures, et cetera. Fluid can often be 
    detected by pressing on one side of the 
    affected joint and at the same time palpat- 
    ing a wavelike fluctuance on the opposite 
    side of the joint.
- Cleanse the skin over the most superficial 
    area of the joint effusion with alcohol and 
    povidone-iodine (Betadine), anesthetize the 
    skin with 1% plain buffered lidocaine, and 
    aspirate as much joint fluid as possible 
    through an 18-20 gauge needle, using 
    aseptic technique throughout. Fluoroscopy 
    may be valuable in guiding needle placement 
    for hip or shoulder joint aspiration.
- Grossly examine the joint aspirate. Clear, 
    light yellow fluid is characteristic of 
    osteoarthritis or mild inflammatory or 
    traumatic effusions. Grossly cloudy fluid 
    is characteristic of more severe inflammat- 
    ion or bacterial infection. Blood in the 
    joint is characteristic of trauma (a 
    fracture or tear inside the synovial 
    capsule) or bleeding from hemophilia or 
    anticoagulants.
- One drop of joint fluid may be used for a 
    crude string or mucin clot test. Wet the 
    tips of two gloved fingers with joint 
    fluid, and repeatedly touch them together 
    and slowly draw them apart. As this 
    maneuver is repeated 10 or 20 times, and 
    the joint fluid dries, normal synovial 
    fluid will form longer and longer strings, 
    usually to 5-10 cm in length. Inflammation 
    inhibits this string formation. This is a 
    non-specific test, but may aid decision at 
    the bed side.
- The essential laboratory tests on joint fluid 
    consist of a Gram stain and culture for 
    possible septic arthritis. (The presence of 
    urate crystals may sometimes be detected on 
    the wet prep or Gram stain.)
- A joint fluid leukocyte count is the next 
    most useful test to order. A count greater 
    than 50,000 white cells/mm^3 is character- 
    istic of bacterial infection (especially 
    when most are polymorphonuclear leuko- 
    cytes). In osteoarthritis, there are 
    usually fewer than 2,000 WBCs/mm^3, and 
    inflammatory arthritis (such as gout and 
    rheumatoid arthritis) falls in the middle 
    range of 2,000-50,000 WBCs/mm^3. If there 
    is more fluid, send to the lab for a 
    glucose level, which will be low in 
    infection compared to serum.
- Obtain x-rays of the affected joint to detect 
    possible unsuspected fractures, or evidence 
    of chronic disease, such as rheumatoid, 
    crystal-induced or osteoarthritis.
- If there is any suspicion of a bacterial 
    infection (based on fever, elevated ESR, 
    cellulitis, lymphangitis, or the joint 
    fluid results above) start the patient on 
    appropriate antibiotics which will have a 
    high concentration in the synovial fluid. 
    The most common, and the most devastating, 
    organism requiring treatment is Staphylo- 
    coccus aureus, which may be adequately 
    treated with oral dicloxacillin or 
    cephalexin 500mg q6h, but, since patients 
    with this infection must be very closely 
    followed, it is usually more practical to 
    admit them to the hospital on intravenous 
    antibiotics. In sexually-active patients, 
    look for gonorrhea. In nursing home 
    patients with urinary tract infections 
    there could be gram-negative organisms. In 
    intravenous drug abusers both staph and 
    gram-negatives.
- Inflammatory arthritis may be treated with 
    non-steroidal anti inflammatory medicat- 
    ions, beginning with a loading dose such as 
    indomethacin (Indocin) 50mg or ibuprofen 
    (Motrin) 800mg, tapered to usual 
    maintenance doses.
- When joint fluid cannot be obtained to rule 
    out infection, it may be a good tactic to 
    treat simultaneously for infectious and 
    inflammatory arthritis.
- Splint and elevate the affected joint and 
    arrange for admission or followup.

What not to do:
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- Do not tap a joint through an area of obvious 
    contamination such as subcutaneous 
    cellulitis. You may innoculate synovial 
    fluid with bacteria.
- Do not be misled by bursitis, tenosynovitis, 
    or myositis without joint involvement. An 
    infected or inflamed joint will have a 
    reactive effusion, which may be evident as 
    fullness, fluctuance, reduced range of 
    motion, or joint fluid which can be drawn 
    off with a needle. It is usually difficult 
    to tap a joint in the absence of a joint 
    effusion.
- Do not instil local anesthetics in the 
    inflammed joint as an ED procedure. They 
    will mask symptoms transiently without 
    treating the underlying problem.
- Do not use NSAIDs when a patient has a 
    history of active peptic ulcer disease with 
    bleeding. Relative contraindications 
    include renal insufficiency, volume 
    depletion, gastritis, inflammatory bowel 
    disease, asthma and congestive heart 
    disease.
- Do not start maintenance NSAID doses for an 
    acute inflammation. It will take a day or 
    more to reach therapeutic levels and pain 
    relief.

Discussion
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The urgent reason for tapping a joint effusion 
is to rule out a bacterial infection, which 
could destroy the joint in a matter of days. 
Beyond identifying an infection (with Gram 
stain, culture, and WBC) further diagnosis of 
the cause of arthritis is not particularly 
accurate nor necessary to decide on acute 
treatment. Reducing the volume of the effusion 
may alleviate pain and stiffness, but this 
effect is usually short-lived, as the effusion 
reaccummulates within hours. Identification of 
crystals is essential for the diagnosis of gout 
or pseudogout, but one acute attack may be 
treated the same as another inflammatory 
arthitis and exact diagnosis deferred to follow 
up.

Infants and young childen may present with 
fever and reluctance to walk from septic 
arthitis of the hip or knee, and arthrocentesis 
may require sedation or general anesthesia.

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 from Buttaravoli & Stair: COMMON SIMPLE EMERGENCIES
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