Trauma and orthopaedic emergencies

Bone and joint infection

Overview and approach

Septic arthritis and osteomyelitis require rapid diagnosis and source-control planning.

  • Conditions covered: osteomyelitis, septic arthritis, and hand flexor tenosynovitis (see Flexor sheath infection and hand bites under Plastics).
  • Children: mostly haematogenous; adults: haematogenous, contiguous (diabetic foot, pressure sores), or post-surgical/implant-related (including prosthetic joint infection, see that page) (1).
  • Learning goals: discuss symptoms and signs of bone and joint infection, and list the diagnostic work-up used to reach a definitive diagnosis.
Assessment and clinical features

Assess fever, local pain, reduced motion, wounds, prosthesis, diabetes and immunosuppression.

  • Children: fever, localised pain, limited movement, refusal to weight-bear or pseudoparalysis of a limb (1)(2).
  • Adults: hot swollen painful joint with painful restricted active and passive movement; osteomyelitis may be subacute with local pain, sinus, or non-healing ulcer. Risk factors: diabetes, immunosuppression, IV drug use, joint disease, prosthesis, recent procedure.
Differentials and investigations

Blood cultures, inflammatory markers, joint aspiration and appropriate imaging; sample before antibiotics when safe, without delaying sepsis treatment.

  • Differentials: transient synovitis, crystal arthritis (gout, pseudogout), inflammatory arthritis, haemarthrosis, trauma, malignancy, Perthes/SUFE.
  • Tests: FBC, CRP/ESR, blood cultures; ultrasound for effusion; MRI when osteomyelitis or abscess is suspected; plain films often normal early (1)(2).
  • Joint aspiration for cell count, Gram stain, culture and crystals before antibiotics when this does not delay treatment of a septic patient (1).
  • Child's hip: Kocher criteria (non-weight-bearing, fever above 38.5 C, ESR above 40, WBC above 12,000); a score of 2-4 warrants urgent orthopaedic assessment, aspiration or MRI (2).
Management and follow-up

Urgent orthopaedic/infectious-diseases management, antibiotics and drainage/debridement as indicated.

  • Urgent orthopaedic review; septic arthritis needs urgent aspiration and/or arthroscopic or open washout (1)(3).
  • Do not delay antibiotics in an ill or rapidly deteriorating patient; start after cultures. Empiric choice depends on age and risk (for example IV cefazolin, adding vancomycin if unwell or MRSA risk in one paediatric guideline) (2).
  • Osteomyelitis: bone biopsy/culture, prolonged therapy, debridement of dead bone or abscess; involve infectious diseases.
  • Follow-up: CRP trend, clinical review, rehabilitation and surveillance for chronic osteomyelitis or growth disturbance.
Red flags and clinical pearls

Normal early inflammatory markers do not exclude infection. A child refusing to weight-bear or a painful prosthetic joint needs prompt review.

  • Septic arthritis is an emergency: cartilage destruction begins within days.
  • Joint replacement, immunosuppression or IV drug use: lower threshold for aspiration and urgent review.
  • Septic hip in a child can mimic transient synovitis: use criteria and low threshold for aspiration.
  • Viva: work-up, aspiration before antibiotics, organisms by age.
References
  1. Royal Children's Hospital Melbourne: Bone and joint infection
  2. Texas Children's Hospital: Acute haematogenous osteomyelitis and/or septic arthritis guideline (2025)
  3. Royal Children's Hospital Melbourne: Osteomyelitis and septic arthritis

Last updated from Sen’s notes on 9 October 2026.