BonE and Joint Infections - Simplifying Treatment in Children Trial

Inclusion Criteria: 1. Children aged 1 to 18 years with acute, uncomplicated, uncomplicated, haematogenous osteomyelitis or septic arthritis 2. Symptoms are present for ≤10 days 3. Osteomyelitis (OM): involvement of long bones of arm or leg AND either pain, point tenderness upon palpation of bone or joint, or difficulty weight bearing; OR Septic arthritis (SA): any of painful and/or swollen large joint; restriction of joint movement; tenderness or warmth. Those with both SA and OM at the same site as the current infection are also eligible. 4. The participant has an elevated C-reactive protein (CRP) ≥20 mg/L or erythrocyte sedimentation rate (ESR) ≥10 mm/h Exclusion Criteria: 1. Infection due to bacteria resistant to cefalexin or atypical infection (e.g. mycobacterial, fungal) 2. Features of sepsis as defined by the presence of organ dysfunction (defined using definitions within the Pediatric Logistic Organ Dysfunction-2 (PELOD-2) score) 3. Concomitant severe, invasive infection e.g. necrotising fasciitis 4. Complicated infection (e.g. presence of prosthetic material; large subperiosteal or intraosseous (either \>3 mm) abscess or soft tissue abscess without surgical intervention; infection secondary to or complicated by trauma) 5. History of allergy to cephalosporin antibiotics or immediate, severe reaction to penicillins 6. Received more than four IV or oral doses of an antibiotic with activity against the likely bacteria causing the current infection 7. Prior episode of osteomyelitis (OM) or septic arthritis (SA) of the same site 8. Prior condition predisposing to poor absorption (e.g. inflammatory bowel disease, current gastrointestinal symptoms) or complicated disease (e.g. immunodeficiency) 9. Prior enrolment in the trial 10. Current recipient of another investigational product as part of a clinical trial