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The limping child
Age directs the diagnosis: toddler — toddler's fracture and septic arthritis; age 3–8 — transient synovitis and Perthes disease; obese adolescent — slipped capital femoral epiphysis (SCFE); and at any age, fever with refusal to bear weight requires exclusion of septic arthritis.
Why it matters in the exam
The classic question compares transient synovitis with septic arthritis of the hip in a 5-year-old. The Kocher criteria help: fever above 38.5°C, refusal to bear weight, ESR above 40 mm/h and white cells above 12,000; a CRP above 2 mg/dL adds to them. The more criteria present, the higher the probability of septic arthritis, and the next step is ultrasound and joint aspiration — not "wait and see".
SCFE is a favourite question: an obese adolescent aged 10–16 with knee or hip pain, a limp and external rotation of the hip on flexion. Diagnosis is by AP and "frog-leg" pelvic X-rays (Klein's line not crossing the epiphysis); treatment is immediate non-weight-bearing and surgical fixation in situ. In 20–40% the disease is bilateral. Perthes disease is idiopathic avascular necrosis of the femoral head in boys aged 4–8, with a painless or mildly painful limp and limited abduction and internal rotation.
Acute osteomyelitis also presents as a limp: usually in the metaphysis of a long bone, S. aureus is the common cause and Kingella kingae in children under 4. The X-ray is normal at first, and MRI is the sensitive test. Night pain, weight loss or blood count abnormalities raise suspicion of malignancy (leukaemia, Ewing sarcoma, osteosarcoma). A toddler's fracture is a spiral tibial fracture after a minor fall.
Key points
- Age 3–8 after a virus, well child — transient synovitis.
- Fever, refusal to bear weight, high ESR and white cells — septic arthritis.
- Obese adolescent with knee pain — SCFE until proven otherwise.
- Perthes: boys aged 4–8, avascular necrosis of the femoral head.
- Night pain and weight loss — exclude malignancy.
Summary table
| Diagnosis | Age and picture | Work-up | Treatment |
|---|---|---|---|
| Transient synovitis | 3–8, after a viral infection, well child, bears weight | Normal or mildly raised markers, small effusion on ultrasound | NSAIDs and rest, improves within days |
| Septic arthritis | Any age, fever, refusal to bear weight, pain on any movement | Kocher criteria, ultrasound, joint aspiration | Urgent surgical washout and IV antibiotics |
| Perthes disease | Boys 4–8, limp with mild pain | X-ray: flattened, dense femoral head | Observation, physiotherapy, sometimes surgery |
| SCFE | Obese adolescent 10–16, hip or knee pain | AP and frog-leg X-rays, Klein's line | Non-weight-bearing and surgical fixation in situ |
| Osteomyelitis | Fever and focal metaphyseal pain | CRP, blood culture, MRI | Antibiotics against S. aureus and Kingella |
| Toddler's fracture | 1–3, minor fall, refuses to bear weight | Tibial X-ray (sometimes normal at first) | Immobilisation |
In the full version for subscribers
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Sources
- Kocher MS et al., Differentiating between septic arthritis and transient synovitis of the hip in children: an evidence-based clinical prediction algorithm, 1999 (validated 2004) — Predictors of septic arthritis
- IDSA/PIDS Clinical Practice Guideline on Acute Hematogenous Osteomyelitis in Pediatrics, 2021 — Diagnosis and antibiotic treatment
- Nelson Textbook of Pediatrics, 22nd edition (2024) — Evaluation of the Child with a Limp; Legg-Calvé-Perthes Disease; Slipped Capital Femoral Epiphysis
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.