A 54-year-old mechanic rests his elbow on the triage counter, the skin over the point of the olecranon stretched shiny and red. He reports three days of swelling after working on a truck, with a temperature of 38.4°C at home but no remembered injury. He can flex and extend the elbow nearly fully, though the lump is tender and warm. The question is whether this is merely inflamed—or infected—and the needle has not yet been placed.

— What’s your move? Read on.

Before you read
  • When is bursal aspiration necessary, and what studies should be sent?
  • Who needs antibiotics, admission, or urgent surgical consultation?

When to Think of It

Focal, fluctuant swelling over a pressure point—most often olecranon or prepatellar—with warmth, erythema, tenderness, or drainage. Consider septic bursitis with fever, rapidly progressive inflammation, overlying cellulitis, immunocompromise, diabetes, skin breakdown, recent procedure, or prior septic bursitis.

Sick or Not Sick

The decisive call is septic versus aseptic bursitis, with extension into the joint or deep tissues. Preserved active and passive joint range of motion favors isolated bursitis; marked pain with passive motion, effusion, or inability to move the joint should shift concern to septic arthritis.

The First Fifteen Minutes

  • Obtain vitals, perfusion assessment, and focused joint examination; outline erythema. If toxic, hypotensive, or meeting sepsis criteria, obtain blood cultures and give balanced crystalloid 30 mL/kg IV, because restoring preload treats hypoperfusion.
  • If septic bursitis is likely and the patient is systemically ill, immunocompromised, or has significant purulence: obtain blood cultures, then give vancomycin 15–20 mg/kg IV over 1–2 hours (dose/interval varies with renal function; check institutional protocol or Lexicomp), because it covers MRSA.
  • Add ceftriaxone 2 g IV once daily when significant cellulitis, systemic illness, or concern for streptococcal/gram-negative coverage exists; it inhibits bacterial cell-wall synthesis. For severe beta-lactam allergy, use clindamycin 600–900 mg IV every 8 hours, but verify local resistance patterns.
  • If stable and uncomplicated after aspiration, oral therapy is reasonable: cephalexin 500 mg PO four times daily, because it covers common MSSA and streptococci. If MRSA risk is substantial, use TMP-SMX DS 1–2 tablets PO every 12 hours; confirm renal function, potassium risk, and local guidance.
  • For painful swelling, use acetaminophen 1,000 mg PO every 6 hours as needed (maximum 4 g/day; use ≤3 g/day with liver disease, heavy alcohol use, or frailty). Avoid corticosteroid injection until infection is excluded.

Definitive Care & Disposition

Aspirate a clinically concerning bursa before antibiotics when this will not delay treatment; send cell count with differential, Gram stain, aerobic/anaerobic culture, and crystals when relevant. Purulent or recurrent bursitis may require repeat aspiration, catheter drainage, or operative bursectomy. Admit for systemic illness, bacteremia, rapidly progressive infection, immunocompromise, inability to take oral therapy, or failure of outpatient treatment. Do not inject a possibly infected bursa. Arrange 24–48-hour reassessment for stable outpatient cases.

How This One Kills

The dangerous error is labeling a warm, fluctuant bursa “traumatic” because the patient still moves the elbow, then injecting corticosteroid into an infected space and accelerating deep infection or bacteremia.
The Differential — What Else Looks Like This
  • Septic arthritis — severe pain with passive joint motion and true intra-articular effusion; confusing it with bursitis risks cartilage destruction and delayed washout.
  • Cellulitis — diffuse, nonfluctuant inflammation without a discrete fluid collection; unnecessary aspiration may injure tissue without obtaining diagnostic fluid.
  • Tophaceous gout — chalky material or recurrent nodules with hyperuricemia history; steroids or antibiotics alone will not address the crystal disease.
  • Olecranon fracture — trauma, bony tenderness, or cortical abnormality on imaging; missing it can lead to displacement and extensor mechanism dysfunction.

The Second-Day Story

Older adults, patients with diabetes, and those taking steroids may have little fever or erythema. A slowly enlarging, mildly tender bursal mass with new functional decline can still be infected, particularly after skin breakdown or a procedure. Trend the examination, inspect carefully for a portal of entry, and lower the threshold for aspiration when the clinical course is changing.
Back to Our Patient
The 54-year-old mechanic has a fluctuant, erythematous olecranon mass but nearly painless passive elbow motion, making isolated septic bursitis more likely than septic arthritis. He is hemodynamically stable, so the team marks the erythema, aspirates the bursa for cell count, Gram stain, culture, and crystals, and begins oral cephalexin while awaiting results because infection is clinically likely. He has no systemic illness or immunocompromise, so he is discharged with compression, activity modification, strict return precautions, and a 24–48-hour reassessment plan; purulence, bacteremia, worsening erythema, or inability to take oral therapy would instead require admission and IV antibiotics.
Patient Presentation to Attending
How you’d present this patient on the floor — tight, pertinent positives and negatives, no rambling
“This is a 54-year-old man with three days of progressively enlarging, warm, painful swelling over the left olecranon and a reported fever to 38.4°C. He has no major trauma, but he frequently leans on that elbow at work and has no history of gout or immunosuppression. He is afebrile and hemodynamically stable here; the bursa is fluctuant and erythematous, with preserved active and passive elbow range of motion and no pain through the joint. There is no crepitus, proximal streaking, or neurovascular deficit. My leading diagnosis is septic olecranon bursitis without current evidence of septic arthritis or systemic toxicity. I plan aspiration for cell count, Gram stain, culture, and crystals, start oral cephalexin, and discharge with 24–48-hour follow-up if he remains stable.”

Study Directive

  • Draw the distinction between bursa, joint, and tendon sheath on an elbow and knee diagram.
  • Practice a verbal “septic versus aseptic” risk assessment using five cases.
  • Review bursal-fluid interpretation and antibiotic selection in your institutional guideline.
  • Perform or observe an ultrasound-guided bursal aspiration and document the approach.