Last reviewed: March 2026
Contents
MDM Templates
Joint Pain NOS
Patient presents with joint pain. They deny fever, recent trauma, and inability to bear weight. Well appearing with non-toxic exam. Joint without significant effusion, warmth, or erythema.
Given history, exam, and workup I have low suspicion for fracture, dislocation, significant ligamentous injury, septic arthritis, gout flare, new autoimmune arthropathy, or gonococcal arthropathy.
Plan: Analgesics.
Disposition: Discharge with return precautions for worsening swelling, fever, or inability to bear weight. Follow up with PCP within 1 week.
Gout / Pseudogout Flare
Patient presents with acute monoarticular pain, swelling, and erythema consistent with crystalline arthropathy. Well appearing without systemic toxicity. Joint aspirated — synovial fluid analysis demonstrates crystals consistent with gout/pseudogout. Gram stain negative.
History and exam lower suspicion for septic arthritis, fracture, and necrotizing soft tissue infection. Synovial fluid analysis supports crystalline arthropathy.
Plan: Colchicine and/or NSAIDs. Intra-articular corticosteroid injection performed for pain relief.
Disposition: Discharge with return precautions for worsening symptoms or fever. Follow up with PCP within 1 week for uric acid management.
Septic Arthritis
Patient presents with acute monoarticular pain, swelling, and inability to bear weight. Febrile. Joint aspirated — synovial fluid appears purulent with elevated WBC count. This is a joint emergency.
History, exam, and synovial analysis concerning for septic arthritis. Empiric IV antibiotics started after joint aspiration and blood cultures obtained.
Orthopedics consulted: Regarding joint aspiration results, need for operative irrigation and debridement, and admission.
Plan: IV antibiotics. Analgesia.
Disposition: Admit for IV antibiotics and likely operative washout.
Clinical Education
Septic Joint Workup
If you’re thinking about septic arthritis, tap the joint. There is no combination of labs, imaging, or clinical features that reliably rules out septic arthritis without synovial fluid analysis. Serum WBC, ESR, and CRP are supportive but not definitive. The only way to know is to look at the fluid.[1]
Send synovial fluid for: cell count with differential, crystal analysis (polarized microscopy), gram stain, and culture. You can do a gram stain with just 1–2 drops — don’t skip it because you got limited fluid.
Blood cultures before antibiotics — positive in ~50% of septic arthritis cases and can guide antibiotic narrowing.
Synovial Fluid Interpretation
| Category | WBC | Appearance | Think |
| Normal | <200 | Clear, straw-colored | Normal |
| Non-inflammatory | 200–2,000 | Clear to slightly cloudy | OA, trauma |
| Inflammatory | 2,000–50,000 | Cloudy, yellow | Gout, pseudogout, RA |
| Septic | >50,000 | Purulent, opaque | Septic arthritis |
The 50,000 threshold is a guideline, not a wall. Gout flares can exceed 50,000 WBC. Partially treated or early septic joints can be below 50,000. The most important thing is the clinical picture — fever + inability to bear weight + hot joint + WBC >50,000 is septic until proven otherwise, even if crystals are also present. Gout and infection can coexist.[1]
Gout Pearls
Acute gout treatment in the ED: NSAIDs (indomethacin 50 mg TID or naproxen 500 mg BID) are first-line. Colchicine (1.2 mg then 0.6 mg one hour later) works best if started within 12–36 hours of flare onset. Intra-articular corticosteroid injection is the fastest-acting option for a single joint — especially useful in patients who can’t take NSAIDs. Oral prednisone (30–40 mg daily x 5 days) is a good alternative for polyarticular flares or patients with contraindications to NSAIDs and colchicine.[2]
Do NOT start or stop allopurinol during an acute flare. Changes in uric acid levels can worsen the flare. Continue it if they’re already on it, defer initiation to the outpatient setting.
Pseudogout (CPPD): Same treatment approach as gout. Look for chondrocalcinosis on X-ray (calcification in the cartilage). Calcium pyrophosphate crystals are rhomboid-shaped and weakly positively birefringent (blue when parallel to the compensator axis) — the opposite of uric acid crystals.
Gonococcal Arthritis
Think gonococcal arthritis in young, sexually active patients with migratory polyarthralgias and skin lesions. The classic presentation is the “triad” of migratory polyarthralgias, tenosynovitis, and painless pustular skin lesions. Synovial fluid culture is positive in only ~25% — also send NAAT from urogenital, pharyngeal, and rectal sites. Treat empirically with ceftriaxone 1g IV/IM daily plus azithromycin 1g PO if clinically suspicious.[3]
Approach to Monoarticular Arthritis
The differential for a hot, swollen joint boils down to three categories: crystal, infection, or structural. Crystal (gout, pseudogout) and infection (septic joint) can look identical on exam — you need synovial fluid to distinguish them. Structural causes (fracture, internal derangement, hemarthrosis) are usually identified by imaging and mechanism.[4]
Risk factors for septic arthritis that should lower your threshold for tapping: prosthetic joint, recent joint procedure, IVDU, immunosuppression, overlying skin infection, and pre-existing joint disease (RA, gout — damaged joints are more susceptible).
References
- Margaretten ME et al. Does this adult patient have septic arthritis? JAMA. 2007;297(13):1478-1488. PubMed
- FitzGerald JD et al. 2020 American College of Rheumatology guideline for management of gout. Arthritis Care Res. 2020;72(6):744-760. PubMed
- Rice PA. Gonococcal arthritis (disseminated gonococcal infection). Infect Dis Clin North Am. 2005;19(4):853-861. PubMed
- Ma L, Cranney A. Approach to acute monoarthritis. Can Fam Physician. 2009;55(9):879-884. PubMed
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