Reasoning GP · Algorithm · 1-page summary
The limping child
For: children aged 0–16 with an acute or chronic limp, in primary care (assessment and first referral). Not for: adults; acute trauma with deformity goes straight to A&E (block 2).
Core rule: a febrile child who will not weight-bear has septic arthritis until proven otherwise. Examine the hip in every child with knee or thigh pain (SUFE), and think of non-accidental injury whenever the injury does not fit the story.
0Stop — call 999 now — before any history
- Toxic or shocked: septic, rigors, high fever, tachycardia, poorly perfused, altered consciousness, airway or breathing concerns → 999
- Spinal cord compression: bilateral leg weakness or back pain with saddle anaesthesia, urinary retention or bladder/bowel dysfunction → 999
- Neurovascular compromise: limb cold, white or blue; or a child who cannot be transferred safely → 999
- Otherwise suspected septic arthritis is Same-day paediatric/orthopaedic, not automatically 999. Do not delay transfer for imaging, bloods or cultures.
1Triage by age — ask the age first
| Age | Think of |
|---|---|
| 0–2 y | DDH, toddler's fracture, septic arthritis, osteomyelitis; always consider abuse if not yet walking |
| 2–5 y | Transient synovitis (still think infection), septic arthritis, toddler's fracture, leukaemia, late DDH |
| 4–10 y | Perthes, transient synovitis, Köhler, JIA, reactive arthritis |
| 10–16 y | SUFE (knee or groin pain), Osgood-Schlatter, overuse, JIA, malignancy |
| Any age | Discitis, fracture, NAI, malignancy, haemophilia, sickle-cell crisis, abdominal/GU causes (incl. torsion) |
2Screen — one row is enough
- Septic arthritis: fever with a hot, swollen or very painful joint, won't weight-bear or marked restriction → Same-day paeds/ortho
- Infant won't move a limb (pseudo-paralysis), fever or not, or acute limp under 3 years → Same-day paediatrics
- SUFE: adolescent, hip/groin/knee pain, restricted internal rotation → Same-day ED/ortho; non-weight-bearing.
- Fracture or osteomyelitis: trauma, deformity, can't weight-bear; toddler's fracture after a trivial bump → Same-day A&E
- NAI: inconsistent story, delayed presentation, bruised pre-mobile infant, injury beyond developmental ability → Same-day safeguarding (practice lead, paediatrics, social care/police by risk). Never discharge with significant concerns.
- Malignancy: persistent bone pain (rest/night), pallor, fatigue, nodes, bruising → FBC ≤48 h; bone swelling/pain → X-ray ≤48 h. Petechiae or hepatosplenomegaly → Immediate referral
3Assess — only once blocks 0–2 are answered
☐ Temp, HR, appearance, pallor, growth centile ☐ Watch the gait; never force walking ☐ Hip: log-roll, internal rotation, leg length ☐ Knee, spine, foot, nodes, abdomen ☐ Neurology both legs (bilateral or UMN → Urgent neurology) ☐ Does the story fit the injury?
X-ray: AP pelvis plus frog-leg lateral of both hips (cross-table if unstable SUFE). Not in primary care: aspiration; ASO titres as a screen.
4Classify — only if the screen is negative
- Transient synovitis — well, post-viral, weight-bearing. Exclusion diagnosis: not if febrile, toxic, non-weight-bearing or marked restriction.
- Perthes — restricted internal rotation, Trendelenburg gait → X-ray; Perthes on X-ray → Paeds ortho <2 weeks. Normal X-ray, still suspected → specialist discussion or MRI.
- JIA / reactive — morning stiffness >30 min, persistent swelling → paeds rheumatology. URTI or gastroenteritis 1–4 weeks before → reactive. Suspected rheumatic fever → Same-day paediatrics
- Mechanical — Osgood-Schlatter, Sever's (heel, 8–12 y), overuse, hypermobility → clinical diagnosis; no X-ray if typical.
- Growing pains — bilateral, night-time, normal exam, never limps by day. Exclusion diagnosis only.
- Uncertain — clinically significant diagnostic uncertainty → Same-day paeds/ortho. Otherwise name reviewer and date.
5Treat today — only these
- Pain: weight-based paracetamol or ibuprofen, lowest effective dose, shortest time — doses: NICE/SPC, BNFC, local formulary. Ibuprofen: avoid if dehydrated; caution in chickenpox or renal disease.
- Pain not controlled: same-day review, not alternating regimens. Codeine contraindicated under 12 (MHRA); strong opioids only in hospital.
- Transient synovitis: relative rest, analgesia, written safety-net. Osgood-Schlatter / Sever's: reduce load (not complete rest), ice or heel raise, gradual return to sport.
- Suspected SUFE: no weight-bearing while transfer is arranged.
6Refer routinely
- Paeds ortho: leg-length difference >1 cm, limp >6 weeks undiagnosed. Suspected DDH → <2 weeks
- Paeds rheumatology: JIA pattern, enthesitis, psoriatic arthritis, recurrent dislocations in hypermobility. Ensure JIA uveitis screening is in place.
- Physiotherapy: Osgood-Schlatter not improving at 6 weeks, hypermobility. CAMHS or pain psychology if chronic pain affects mood or school.
7Never reassure by
- A normal temperature, CRP, ESR or WCC, or a low Kocher score.
- A normal knee examination in knee or thigh pain — examine the hip.
- A normal AP X-ray: SUFE needs a lateral view; early Perthes may need MRI.
- No fever in a neonate or infant who will not move a limb.
- A normal first blood film — blasts may be absent in early leukaemia.
- A story that does not fit the injury or the child's developmental ability.
8Safety-net — verbally and in writing, then document it
999 “Call 999 if your child collapses, can't breathe, is extremely pale with leg pain, or the leg goes cold, white or blue.” Same-day A&E “Go today if a fever over 38°C develops, they stop weight-bearing, the joint becomes hot, red or swollen, or they are vomiting or getting more unwell.”
Back to GP within 48 h: “Not improving, new symptoms, night or rest pain, or they are not right.” Transient synovitis: review 24–48 h and at 1 week; not resolved → X-ray hip + Urgent paeds ortho; never discharge.
✓Safe to leave primary care only if — all five, documented
No block 0–2 row applies, incl. no safeguarding concern
Systemically well, afebrile, weight-bearing, no marked hip restriction
Gait seen and hip examined; one benign cause, or uncertainty stated
Review booked (24–48 h for transient synovitis) with owner
Written safety-net given and documented
Summary of the full Reasoning GP limping child algorithm, which holds the detail, examination, investigations and evidence. Sources: NICE NG12 (updated April 2026); BOAST septic arthritis and SUFE; RCPCH/paediatric ophthalmology JIA uveitis screening; BSPAR; MHRA codeine advice. Clinical reference — follow local paediatric and safeguarding policies and check doses in the current BNFC.