Septic Arthritis vs Bursitis
Septic Arthritis and Bursitis are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.
Septic Arthritis vs Bursitis at a glance
- Septic Arthritis: Bacterial infection of a joint — orthopedic emergency requiring urgent arthrocentesis and drainage.
- Bursitis: Inflammation of a synovial bursa from repetitive pressure, trauma, crystal disease, or infection.
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Side-by-side comparison
| Feature | Septic Arthritis | Bursitis |
|---|---|---|
| At a glance | Bacterial infection of a joint — orthopedic emergency requiring urgent arthrocentesis and drainage. | Inflammation of a synovial bursa from repetitive pressure, trauma, crystal disease, or infection. |
| Classic presentation | Acute monoarticular pain, swelling, warmth, erythema; Markedly reduced range of motion; Fever, chills (variable — fever absent in up to 40%); Migratory polyarthralgia, tenosynovitis, and pustular rash suggest disseminated gonococcal infection; Joint effusion with warmth and erythema; Extreme pain on passive motion (vs bursitis where… | Olecranon bursitis classically produces a goose-egg over the posterior elbow with full elbow flexion and extension — the hallmark feature that distinguishes it from septic arthritis.; Localized swelling and discomfort over a bony prominence; Pain with direct pressure (kneeling, leaning) and at end-range motion; Trochanteric pain… |
| Workup / key labs | Arthrocentesis BEFORE antibiotics when possible (do not delay antibiotics if patient septic):; • WBC count, differential (typically >50,000 with >75% PMNs; gonococcal often lower); • Gram stain (sensitivity ~50%); • Bacterial culture (aerobic and anaerobic); • Crystals on polarized microscopy; Blood cultures × 2 sets (positive in ~50%);… | Aspirate fluctuant superficial bursae when infection is suspected: send fluid for Gram stain, culture, cell count with differential, and crystal analysis. Bursal fluid WBC >2,000-5,000/mm3 with neutrophil predominance and positive Gram stain or culture confirms septic bursitis.; CBC with differential, ESR, and CRP if septic bursitis is… |
| Imaging | Plain radiographs — baseline; usually unremarkable acutely; soft tissue swelling, joint effusion; Ultrasound — guides aspiration, especially for deep joints (hip); MRI — if osteomyelitis suspected or to evaluate axial joints (SI, sternoclavicular) | Clinical diagnosis in most cases; imaging not routinely required; Plain radiographs if trauma, foreign body, or chronic refractory symptoms (look for fracture, calcific deposits, olecranon spur); Ultrasound differentiates bursal fluid from intra-articular effusion and guides aspiration; MRI for refractory greater trochanteric pain… |
| First-line treatment | Empiric antibiotics: Vancomycin to cover MRSA (or daptomycin/linezolid if vancomycin contraindicated); Empiric antibiotics: Add gram-negative coverage based on host: ceftriaxone (community), cefepime or pip-tazo (immunocompromised, healthcare-associated); Empiric antibiotics: Sexually active young adult with disseminated features:… | Activity modification, padding, and avoidance of direct pressure; Ice and NSAIDs — ibuprofen, naproxen, or diclofenac for 7-14 days; Compressive wrap for superficial bursae; Bursal aspiration for symptomatic effusion and to obtain diagnostic fluid; Physical therapy with hip abductor strengthening and iliotibial band stretching for… |
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