Pediatric Limp

Key considerations: Septic arthritis, Osteomyelitis, Legg-Calve-Perthes disease

Cannot miss

history: Acute vs chronic onset; Trauma history; Fever, recent illness (post-infectious synovitis); Night pain or pain at rest (red flag for malignancy); Weight loss, fatigue (systemic illness); Age-specific: toddlers (toddler fracture, NAT), school-age (Perthes, transient synovitis), adolescents (SCFE, Osgood-Schlatter); exam: Observe gait pattern: antalgic, Trendelenburg, circumduction; Range of motion of hip, knee, ankle — where is the pain?; Hip internal rotation — limited and painful in septic hip, SCFE, Perthes; Joint effusion: warmth, swelling, erythema; Spine and SI joint exam; Full skin survey if NAT concern; Abdominal exam (psoas irritation from appendicitis can cause limp); labs: CBC, CRP, ESR (Kocher criteria for septic hip); Blood culture if febrile; Consider LDH, uric acid, peripheral smear if malignancy suspected; imaging: X-ray of affected area (AP and lateral); Hip X-ray: frog-leg lateral view (SCFE — may only be visible on frog-leg); Ultrasound: hip effusion (compare sides); MRI if osteomyelitis suspected and X-ray normal; bedside: Point-of-care ultrasound for joint effusion; Arthrocentesis of joint if septic arthritis suspected

immediate: If septic arthritis suspected: do NOT delay antibiotics for imaging — aspirate joint and start empiric antibiotics; NPO if joint aspiration or surgical washout likely; general: Apply Kocher criteria for hip: fever, non-weight-bearing, ESR >40, WBC >12k — probability of septic hip increases with each criterion; specific: diagnosis: Transient synovitis; steps: NSAIDs: ibuprofen 10mg/kg q6-8h; Rest and limited weight-bearing; Follow-up in 24-48 hours — should be improving; If not improving in 48 hours, reconsider diagnosis (Perthes, early septic); diagnosis: Septic arthritis; steps: Urgent joint aspiration (>50k WBC in synovial fluid); IV antibiotics: cefazolin 25-30mg/kg q8h (add vancomycin if MRSA prevalence high); Orthopedic consult for operative washout; Admission for IV antibiotics; diagnosis: SCFE; steps: NON-WEIGHT-BEARING immediately (risk of further slip); Orthopedic consult for urgent in-situ pinning; Check contralateral hip (bilateral in 20-40%); Screening labs: thyroid, growth hormone if atypical presentation

admit: Septic arthritis; SCFE (non-weight-bearing + surgery); Osteomyelitis; Suspected malignancy; NAT workup; discharge: Transient synovitis with improving symptoms; Toddler fracture with orthopedic follow-up; Soft tissue injury with clear mechanism; Follow-up arranged within 24-48 hours; consults: Orthopedics for septic arthritis, SCFE, osteomyelitis; Oncology if malignancy suspected; Child abuse team if NAT suspected

Kocher criteria for septic hip: fever, non-weight-bearing, ESR >40, WBC >12k — 4/4 criteria = 99.6% probability of septic arthritis
SCFE: obese adolescent with hip pain — ALWAYS get frog-leg lateral view. Knee pain can be the ONLY presenting complaint (referred pain)
Transient synovitis vs septic arthritis: CRP is the single best lab — CRP <20mg/L makes septic arthritis very unlikely
Toddler fracture: spiral fracture of tibia in toddler from twisting mechanism — initial X-ray may be negative, repeat in 7-10 days if clinical suspicion high

Kocher Criteria (JBJS 1999), Pediatric Orthopedics (Herring), Pediatric Emergency Medicine (Fleisher & Ludwig). Last reviewed: 2024-11-01