bone and joint infections
in review
5 min read
Updated 2026-09-29
bone and joint infections
Native septic arthritis: aspirate before antibiotics, drain the joint, cover S. aureus (± Gram-negatives/gonococcus by risk). Vertebral osteomyelitis: MRI; if stable and blood cultures negative, biopsy before antibiotics; 6 weeks of therapy (Bernard (2015)). Prosthetic joint infection: aspirate before antibiotics; debridement with implant retention (DAIR) only for early infection with a stable implant; rifampin combination for staphylococci; 12 weeks beats 6 (DATIPO (2021)). Oral step-down with highly bioavailable agents is non-inferior to IV (OVIVA (2019)).
do not miss
- spinal epidural abscess (back pain + fever + any neurological deficit) → urgent MRI whole spine and spinal surgery
- hot swollen joint = septic arthritis until aspirated — crystals do not exclude infection
local antibiogram
Empiric S. aureus cover depends on local MRSA rates; Gram-negative cover (people who inject drugs, immunocompromised, elderly) follows local ceftriaxone/cefepime susceptibility.
native septic arthritis
diagnosis
- aspirate before antibiotics: cell count, Gram stain, culture, crystals; synovial WBC >50 × 10⁹/L strongly suggests infection (lower counts do not exclude it)
- blood cultures ×2; gonococcal NAAT (urine/genital, pharynx, rectum) in sexually active patients
- risk: prior joint disease (RA, gout), prosthesis, diabetes, IDU, immunosuppression, bacteraemia, skin breach
management
- drainage: needle aspiration (repeated), arthroscopic, or open — outcomes similar; hip → orthopaedics
- empiric by Gram stain:
| Gram stain / setting | empiric |
|---|---|
| GPC | cefazolin 2 g IV q8h; vancomycin if MRSA risk |
| GNB | ceftriaxone 2 g IV q24h; cefepime if IDU or immunocompromised (Pseudomonas) |
| negative stain, high risk | vancomycin + ceftriaxone |
| sexually active, polyarthralgia/tenosynovitis/pustules | ceftriaxone 1 g IV q24h — see gonorrhoea, chlamydia, and other STIs |
- duration: 2 weeks after surgical drainage non-inferior to 4 in a mostly hand/wrist cohort (Gjika (2019)); large joints or S. aureus bacteraemia usually 3–4 weeks — oral step-down once improving
- S. aureus bacteraemia → full S. aureus bacteraemia work-up including TTE
native vertebral osteomyelitis (IDSA 2015)
diagnosis
- new or worsening back pain + fever or raised CRP/ESR, especially with bacteraemia, IDU, recent spinal procedure, or endocarditis
- MRI spine (whole spine if epidural abscess suspected); blood cultures ×2; Brucella serology if endemic exposure; IGRA ± CT-guided biopsy AFB culture if TB risk
- S. aureus, S. lugdunensis, or Candida in blood → presumptive pathogen, no biopsy needed
- otherwise CT-guided biopsy (culture + histology) — withhold antibiotics if haemodynamically stable and neurologically intact; if first biopsy negative, repeat or proceed to open biopsy
- S. aureus, streptococcal, or enterococcal bacteraemia → echocardiography
management
- unstable or neurological deficit → empiric vancomycin + ceftriaxone (cefepime if Pseudomonas risk) after blood cultures
- targeted therapy per organism; 6 weeks total (Bernard (2015): 6 weeks non-inferior to 12); longer for undrained abscess or MRSA
- surgery: neurological deficit, epidural abscess with cord/cauda compression, instability, progression despite therapy
- follow clinically and with CRP; routine repeat MRI not recommended — imaging lags clinical response
prosthetic joint infection
classification
| type | timing | typical organisms |
|---|---|---|
| early | <3 months after surgery | S. aureus, Gram-negatives |
| delayed (low-grade) | 3–12(–24) months | CoNS, Cutibacterium — pain, loosening, few systemic signs |
| late haematogenous | >1–2 years, acute onset | S. aureus, streptococci — look for bacteraemia source |
diagnosis (ICM 2018)
- major criteria (either = PJI): sinus tract communicating with the prosthesis; same organism in ≥2 periprosthetic cultures
- minor criteria (scored): raised CRP, ESR, D-dimer; synovial WBC and PMN%, leucocyte esterase, alpha-defensin; single positive culture; histology
- aspirate before antibiotics; if stable, hold antibiotics ≥2 weeks to improve culture yield
- intraoperative: 3–5 tissue samples; sonication of explanted components
surgical strategy
| strategy | when |
|---|---|
| DAIR (debridement, antibiotics, implant retention) + polyethylene exchange | symptoms <3 weeks or implant <30 days, well-fixed implant, no sinus tract, organism treatable with biofilm-active agent |
| one-stage exchange | chronic infection, known susceptible organism, good soft tissue |
| two-stage exchange | chronic infection, sinus tract, resistant or unknown organism, poor soft tissue |
| resection / arthrodesis / amputation | failed exchanges, non-reconstructable |
| chronic suppression | retained infected implant, unfit for surgery |
antibiotics
- staphylococci + retained hardware (DAIR, one-stage): β-lactam (cefazolin/cloxacillin) or vancomycin + rifampin 2–6 weeks IV → oral fluoroquinolone (or other) + rifampin
- rifampin never alone (rapid resistance); start once bacteraemia cleared and wound dry; check interactions
- total 12 weeks — DATIPO (2021): 6 weeks inferior to 12 (more persistent infection); IDSA allowed 3 months (hip) to 6 months (knee) after DAIR
- two-stage exchange: typically 6 weeks between stages
oral therapy
OVIVA (2019): switching to oral within the first 7 days was non-inferior to 6 weeks IV for 1-year treatment failure across native bone/joint, spine, and implant infections.
- suitable agents: fluoroquinolones, TMP-SMX, linezolid, doxycycline, clindamycin, rifampin (combination) — per susceptibility and bioavailability
- avoid if bacteraemia uncontrolled, endocarditis, or unreliable absorption/adherence
Diabetic foot osteomyelitis: see skin and soft tissue infections.
traps
- starting antibiotics before joint aspiration or spinal biopsy in a stable patient
- attributing a hot joint to gout because crystals are present
- repeating MRI to judge early response in vertebral osteomyelitis
- rifampin monotherapy, or rifampin started with a large uncontrolled bacterial load
- DAIR for chronic PJI or a loose implant — high failure
- 6 weeks for PJI treated with implant retention — DATIPO favours 12
- missing endocarditis in S. aureus vertebral osteomyelitis