Paediatrics · Full case
Childhood Limp
The Limping Child · Clinical Reasoning Framework v2
GP & SCA · Age-based differential · septic arthritis · transient synovitis · Perthes' · SUFE · DDH · hip refers to knee · NG12 leukaemia · safeguarding
Age frames the differential0–3y: DDH, septic arthritis, toddler's fracture, non-accidental injury. 3–10y: transient synovitis, septic arthritis, Perthes'. 10–16y: SUFE, septic arthritis, Perthes'. Septic arthritis & malignancy can occur at any age. Age narrows the list dramatically
Septic arthritis = emergencyA child who won't weight-bear or move the joint, with fever and systemic upset, has septic arthritis until proven otherwise — an emergency needing same-day assessment, joint aspiration and IV antibiotics. Kocher criteria (non-weight-bearing, fever >38.5, ESR/CRP↑, WCC↑) help differentiate from transient synovitis
The hip refers to the kneeA child with knee or thigh pain and a normal knee must have the HIP examined — SUFE and Perthes' classically present with knee/thigh pain. Missing this is the commonest, most dangerous error in the limping child
SUFE — don't miss itSlipped upper femoral epiphysis: typically an overweight adolescent (often around puberty), with hip/groin/thigh/knee pain, an externally rotated leg and limited internal rotation. Needs urgent orthopaedics and non-weight-bearing — delay causes avascular necrosis. Can be bilateral
Transient synovitis is a diagnosis of exclusionThe commonest cause of acute limp in 3–10y — often post-viral, the child is systemically well, afebrile or low-grade, and improves over days. But it is diagnosed only after excluding septic arthritis; never assume it in a febrile, unwell, non-weight-bearing child
🟣 Persistent bone pain → leukaemiaNICE NG12: unexplained persistent bone pain, limp or musculoskeletal symptoms with systemic features — pallor, bruising/petechiae, hepatosplenomegaly, generalised lymphadenopathy, fever — warrant a very urgent FBC (within 48h) and immediate paediatric referral for suspected leukaemia. Night pain & bone tenderness are clues
Think safeguardingAlways consider non-accidental injury — inconsistent or changing history, injury not matching development/mechanism, delayed presentation, other injuries, or a non-mobile child with a fracture. A limp can be the presentation of abuse
Other causesReactive/juvenile idiopathic arthritis, osteomyelitis, trauma/toddler's fracture, discitis, soft-tissue/foot causes, growing pains (bilateral, night, never limps by day, normal exam — a diagnosis of exclusion). Don't forget the foot, ankle and whole leg, and a full systemic look
📋 Clinical Stem — The Limping Child
A 13-year-old boy with a few weeks of "knee" pain and a limp, now worse, who is overweight and walks with his foot turned out — and whose knee examines completely normally
Kyle Morrison, 13, is brought by his mother with several weeks of right knee and thigh pain and a limp that has worsened over the past week, now making PE difficult. There was no clear injury. He is overweight for his age. He walks with an antalgic gait and the right leg appears externally rotated. When you examine the knee it is entirely normal — no swelling, full painless range. He is otherwise well, afebrile, with no rash, bruising, weight loss or night sweats, and no recent illness. His mother is frustrated that "it's just his knee" and wants a referral to physiotherapy.
This stem tests the single most important principle of the limping child — that the hip refers to the knee — and the recognition of slipped upper femoral epiphysis (SUFE): an overweight adolescent around puberty, with knee/thigh pain, an externally rotated leg, restricted internal rotation of the hip, and a normal knee. It requires the candidate to examine the HIP despite knee-presenting pain, to recognise SUFE as needing urgent orthopaedic referral and non-weight-bearing (to prevent avascular necrosis), and NOT to refer to physiotherapy or reassure as a knee problem. It also tests the broader age-based framework and the exclusion of the emergencies (septic arthritis, and the NG12 leukaemia red flags) and safeguarding. The SCA challenge is to redirect a parent fixated on "the knee" toward urgent hip assessment, and to convey the seriousness without alarm.
Scenario A — SUFE (this stem) Overweight adolescent, knee/thigh pain, externally rotated leg, restricted hip internal rotation, normal knee. Urgent orthopaedics, non-weight-bearing, X-ray (AP + frog-lateral); avoid AVN; check the other hip.
Scenario B — Septic arthritis (EMERGENCY, any age) Won't weight-bear/move joint, fever, systemically unwell, raised inflammatory markers (Kocher). Same-day admission; aspiration + IV antibiotics.
Scenario C — Transient synovitis (3–10y) Well child, post-viral, low/no fever, improving; diagnosis of exclusion after ruling out sepsis. Rest, analgesia, safety-net, review.
Scenario D — Perthes' (3–10y) Insidious limp/hip-knee pain, restricted hip movement, often well. Orthopaedic referral; X-ray (avascular necrosis of the femoral head).
Scenario E — Red flags: leukaemia / DDH / NAI Persistent bone pain + pallor/bruising/lymphadenopathy/fever → very urgent FBC + paediatrics (NG12 leukaemia). Infant: DDH (asymmetry, limited abduction). Any: non-accidental injury — inconsistent history/other injuries.
Key variables to adapt for Age (DDH/septic/toddler's # → transient synovitis/Perthes' → SUFE); weight-bearing & systemic features (septic); hip refers to knee; SUFE in the overweight adolescent; persistent bone pain + systemic features (leukaemia, NG12); safeguarding/NAI; growing pains as exclusion; bilateral/other-hip involvement.
Steps:
1
Step 1
History — Age · Weight-Bearing & Systemic Features · Red Flags · Safeguarding · ICE
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The history is structured around age (which reshapes the differential), the two pivotal questions — is the child weight-bearing, and is the child systemically well? — and the red flags (septic arthritis, the NG12 leukaemia features, and safeguarding). The over-arching rule, which Kyle's case turns on, is that knee or thigh pain in a child demands assessment of the hip.
🎓 SCA framing — redirect "it's just his knee" to the hip
"I can see why you think it's his knee — that's where it hurts. But in children, hip problems very often show up as knee pain, so I'm going to examine his hip carefully too. That's important, because some hip conditions need treating quickly."
The parent (and the symptom) point at the knee. The skill is to explain, not dismiss, why the hip must be examined — and to act urgently if SUFE is found, rather than refer to physiotherapy.
1A — Age, weight-bearing, systemic features, red flags
1B — Red flags
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Red Flags — the limping child you cannot miss
| Red flag | Why dangerous | Action |
|---|---|---|
| Septic arthritis / osteomyelitis — won't weight-bear/move joint, fever, systemically unwell | Joint destruction within days; sepsis; an emergency at any age. | Same-day paediatric/orthopaedic admission; aspiration + IV antibiotics (Kocher to support) |
| SUFE — overweight adolescent, hip/thigh/knee pain, externally rotated leg, ↓ internal rotation | Delay causes avascular necrosis and permanent damage; can be bilateral. | Urgent orthopaedic referral; non-weight-bearing; X-ray (AP + frog-lateral) |
| 🟣 Leukaemia — persistent bone pain/limp + pallor, bruising/petechiae, hepatosplenomegaly, lymphadenopathy, fever, night pain | Haematological malignancy presenting as bone/joint pain. | Very urgent FBC (within 48h) + immediate paediatric referral — NICE NG12 |
| Non-accidental injury — inconsistent/changing history, other injuries, non-mobile child with fracture | Child protection. | Safeguarding assessment per local child-protection pathway |
| Perthes' / DDH — insidious limp, restricted hip movement (Perthes' 3–10y); infant asymmetry/limited abduction (DDH) | Femoral head/hip joint damage if missed. | Orthopaedic referral; hip X-ray/USS |
| Atraumatic limp under 3 / unable to localise | Young children localise poorly; serious causes (septic, NAI, malignancy) easily missed. | Low threshold for assessment/investigation/paediatrics |
1C — ICE
💭 Ideas
"What do you think is causing it — and what were you hoping we'd do?"
Kyle's mother thinks it's a knee problem for physiotherapy. Surfacing this lets you explain, respectfully, why the hip must be examined and why a referral to physio would be the wrong move if this is SUFE — replacing her plan with a better one she understands.
😟 Concerns
"Has anything about it worried you, beyond the pain and the limp?"
She may worry about him missing school/sport, or (unspoken) something serious. Naming it lets you reassure appropriately while being honest that some hip conditions need urgent attention.
🎯 Expectations
"Let me explain what I've found and what needs to happen next."
She expects a physio referral. If SUFE is found, you must reframe to urgent hospital assessment and non-weight-bearing — clearly and calmly, so she understands the change of plan and its importance.
1D — Psychosocial context
🦵 "It's just his knee"
Explain why the hip matters, without dismissing.
"You're right that the pain's in his knee — but in growing children the hip often sends its pain to the knee, so checking the hip is exactly how we avoid missing something important."🏥 Reframing to urgent care
If SUFE, explain the change of plan calmly.
"From examining his hip, I'm concerned about a condition where the top of the thigh bone slips. It needs the hospital to see him urgently today, and he shouldn't put weight on that leg in the meantime — treating it quickly protects the hip."🚫 Not physiotherapy
Explain why physio would be wrong here.
"I know you were hoping for physio, but if this is what I think, exercises could make it worse — this needs an orthopaedic surgeon, not physiotherapy, and quickly."🛡️ Honest reassurance
Balance seriousness with calm.
"This is treatable, and we've caught it at the right time by checking properly. I'll arrange everything now and explain each step so you know what's happening."🎓 SCA Checkpoint — Step 1TasksRelating to OthersGlobal Skills
Key phrases that score
"In children, hip problems often show up as knee pain — so I'll examine his hip." — the central principle.
"Can he bear weight, and has he had any fever?" — the septic-arthritis screen.
"Any night pain, pallor, bruising, or lumps?" — the NG12 leukaemia screen.
Deductions
- Examining only the knee; missing SUFE / not examining the hip
- Not screening for septic arthritis (weight-bearing/fever) or leukaemia red flags
- Referring to physiotherapy / reassuring as a knee problem
- Not considering safeguarding / age-based differential
🔴 Red
Treats as a knee problem; no hip exam; SUFE missed; physio referral; no septic/leukaemia/safeguarding screen
🟠 Amber
Examines hip; suspects a hip cause; some red-flag screen; urgency/age framework partial; ICE partial
🟢 Green
Reasons by age; examines the hip for knee pain; recognises SUFE → urgent ortho + non-weight-bearing; screens septic/leukaemia/safeguarding; reframes parent; ICE all three
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Step 2
Triage — Emergency (Septic/Leukaemia/NAI) · Urgent (SUFE/Perthes) · Routine
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Triage the limping child by danger: septic arthritis, suspected leukaemia and safeguarding are same-day; SUFE and Perthes' are urgent orthopaedic referrals; transient synovitis and minor causes are managed/reviewed in primary care — but only once the emergencies are excluded. Kyle is in the urgent SUFE lane.
🔴 Emergency
Same day
Don't delay- Septic arthritis / osteomyelitisWon't weight-bear + fever/unwell → admit
- 🟣 Suspected leukaemiaBone pain + systemic features → very urgent FBC + paediatrics (NG12)
- Safeguarding / NAIChild-protection pathway
🟠 Urgent
Orthopaedics
Days- SUFEUrgent ortho; non-weight-bearing; X-ray (Kyle)
- Perthes'Orthopaedic referral; X-ray
- DDH (infant)Hip USS/X-ray; orthopaedics
🟢 Routine
Primary care
After exclusion- Transient synovitisWell child; rest/analgesia; safety-net; review
- Minor trauma/soft-tissueConservative; review
- Growing pains (exclusion)Reassure if classic & normal exam
🎓 SCA Checkpoint — Step 2Tasks
Triage rationale
"He's not feverish or systemically unwell, which is reassuring against infection — but the hip findings make me concerned about a slipped growth plate, which is an urgent orthopaedic problem, not a physio one."
Deductions
- Routing SUFE to physiotherapy/routine care
- Missing septic arthritis or leukaemia red flags
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Step 3
Examination — Gait · The HIP (Internal Rotation) · Whole Leg · Systemic
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Examination must include the hip even when the knee is the complaint — gait, the look/feel/move of the hip with particular attention to internal rotation (lost early in SUFE and hip disease), the whole leg and the joint above and below, plus a systemic examination for the sinister causes.
🎓 SCA Checkpoint — Step 3TasksGlobal Skills
Narration that scores
"I'll watch him walk, examine his hip — especially rotating it inwards — as well as the knee and the whole leg, and check him over generally for anything else, like glands or bruising."
Deductions
- Examining only the knee; not testing hip internal rotation
- No systemic exam for leukaemia/safeguarding signs
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Step 4
Investigations — Imaging (Frog-Lateral) · Bloods · FBC for Red Flags
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Investigations are directed by the suspected cause: hip X-ray (AP + frog-lateral) for SUFE/Perthes'; inflammatory markers and a very urgent FBC for the emergencies (septic arthritis, leukaemia); and ultrasound for effusion/DDH — though many decisions (admit/refer) are made clinically and shouldn't wait for tests.
🎓 SCA Checkpoint — Step 4Tasks
Key reasoning
"The orthopaedic team will get a specific hip X-ray (a 'frog-leg' view) that shows a slipped growth plate. If a child looked feverish or unwell I'd also be arranging urgent blood tests for infection — and a very urgent blood count if I were worried about anything in the blood."
Deductions
- Forgetting the frog-lateral view for SUFE
- Not arranging urgent FBC when leukaemia features are present
- Waiting for tests instead of admitting suspected septic arthritis
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Step 5
Diagnosis — By Age & Pattern · The Dangerous Masqueraders
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Reach the diagnosis through age, weight-bearing/systemic status and examination — and consciously hold the dangerous masqueraders (SUFE behind "knee pain", septic behind "viral limp", leukaemia behind "growing pains").
🚩 The one rule that saves the case
Examine the hip in a child with knee pain. Kyle's formulation is SUFE — an overweight 13-year-old with knee/thigh pain, an externally rotated leg, restricted hip internal rotation and a normal knee — needing urgent orthopaedic referral and non-weight-bearing to prevent avascular necrosis, NOT physiotherapy. The same discipline (reason by age, screen the emergencies, examine the joint above) catches the septic hip, Perthes', DDH and the leukaemia/safeguarding red flags.
🎓 SCA Checkpoint — Step 5Tasks
Explaining it plainly
"His knee is fine — the problem is in his hip. It looks like the growth plate at the top of the thigh bone has slipped, which is why his leg turns out and his hip is stiff. It's treatable, but he needs to be seen by the bone specialists urgently and not put weight on the leg."
Deductions
- Diagnosing a knee problem; missing SUFE
- Calling it transient synovitis/growing pains without exclusion
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Step 6
Referral — Emergency Paediatrics · Urgent Orthopaedics · 2WW (Leukaemia) · Safeguarding
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Referral is danger-led: emergency paediatrics/orthopaedics for septic arthritis; very urgent paediatrics + FBC for suspected leukaemia (NG12); urgent orthopaedics for SUFE/Perthes'/DDH; and the safeguarding pathway where abuse is suspected.
🎓 SCA Checkpoint — Step 6Tasks
Decisive action
"I'm referring Kyle to the orthopaedic team urgently today — I'll call them, and in the meantime he must not put weight on that leg. I'll arrange how he gets there safely."
Deductions
- Referring SUFE to physiotherapy/routine
- Not admitting septic arthritis / not escalating leukaemia features
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Step 7
Management — By Cause · Non-Weight-Bearing · Safety-Net · Support the Family
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Management is cause-specific and, for the emergencies, is mostly about timely recognition and the right referral: non-weight-bearing and urgent orthopaedics for SUFE; admission for septic arthritis; supportive care with safety-netting for transient synovitis; and clear family communication throughout.
🎓 SCA Checkpoint — Step 7TasksRelating to OthersGlobal Skills
A plan that scores
"So for Kyle: urgent orthopaedic referral today, no weight on the leg, and I'll sort how he gets to hospital. (For a well child with likely transient synovitis: rest, child-dose ibuprofen, and come straight back if he develops a fever, won't put weight on it, or isn't better within a few days.)"
Deductions
- Allowing weight-bearing in SUFE; physio referral
- No safety-net for transient synovitis
- Over-labelling "growing pains" without exclusion
Childhood Limp — SCA Consultation Scorecard
Age-based · hip refers to knee · SUFE · septic arthritis · NG12 leukaemia · safeguarding
0/ 33 pts
Global Skills
Structure, language, responsiveness
0/7
Tasks
Clinical reasoning, diagnosis, management
0/15
Relating to Others
Communication, rapport, shared decisions
0/11
RAG Self-Assessment
🔴 Red
Treats as knee; no hip exam; SUFE missed → physio; septic/leukaemia/safeguarding not screened; no safety-net
🟠 Amber
Examines hip; suspects hip cause; some red-flag screen; urgency/age framework partial; ICE partial
🟢 Green
Age-based reasoning; hip examined for knee pain; SUFE → urgent ortho + non-weight-bearing; septic/leukaemia/safeguarding screened; parent reframed; ICE all three; safety-net
Complete the checklist to see your score and feedback
"It's Kyle's knee — he's had pain in it for a few weeks and now he's limping and can't do PE. I think he just needs some physio for it, can you refer him?"
Who you are (Kyle's mother)
You've brought your son Kyle, 13, with several weeks of right knee and thigh pain and a limp that's got worse this past week. No clear injury. He's a bit overweight for his age. You're convinced it's a knee problem and want a physiotherapy referral so he can get back to sport. You're slightly impatient and feel it's "obviously his knee".
Hidden concerns (reveal if explored)
Frustration: you feel it's been going on too long and just want it sorted with physio.
Worry (if the doctor seems concerned): you become anxious if told it might be serious — you'll need clear, calm explanation and reassurance it's treatable.
Practicalities: you worry about him missing school and how you'll get to hospital.
Clinical details if asked
- Knee/thigh pain several weeks, worsening; limp; no injury; can still bear weight (limping)
- Overweight; around pubertal age; otherwise well
- No fever, no recent illness, no night pain, no pallor/bruising/lumps, no weight loss/night sweats
- Walks with the right leg/foot turned outwards (you've noticed he "walks funny")
- On examination: knee is normal; the hip is stiff and uncomfortable when rotated inwards
Reactions at key moments
- If the doctor only examines the knee & offers physio: you're satisfied — so a strong candidate must examine the hip and NOT do this.
- On "I need to check his hip": mildly surprised ("but it's his knee"), accepting when explained.
- On the SUFE explanation & urgent referral: anxious but reassured by calm clarity and that it's treatable.
- On non-weight-bearing: you accept it once you understand why.
- Challenge line: "Are you sure? It really seems like it's just his knee — can't he just have physio?"
"I really think you're overcomplicating this — it's his knee, he just needs physio and to rest it. Why are you sending him to hospital?"
Resolution: The consultation succeeds if the GP: (1) reasons by age and applies the rule that the hip refers to the knee — examining the hip despite a knee complaint; (2) recognises SUFE (overweight adolescent, externally rotated leg, restricted hip internal rotation, normal knee) and arranges urgent orthopaedic referral with non-weight-bearing, NOT physiotherapy; (3) screens and excludes septic arthritis (weight-bearing/fever) and the NG12 leukaemia red flags, and considers safeguarding; (4) reframes the mother's expectation calmly and clearly, conveying urgency without alarm; (5) safety-nets and supports the family practically. It fails if the GP examines only the knee and refers to physiotherapy, missing SUFE.
Clinic Quick Reference
The Limping Child — Clinical Decision Framework
Age-based · hip refers to knee · exclude the emergencies
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👶 1 — Differential by age
0–3y: DDH, septic arthritis, toddler's fracture, NAI. 3–10y: transient synovitis, septic arthritis, Perthes'. 10–16y: SUFE, septic arthritis, Perthes'. Any age: septic arthritis, malignancy (leukaemia), osteomyelitis, JIA, NAI. Always examine the hip in knee pain (SUFE/Perthes' refer to the knee).
🚦 2 — Triage & act
🔴 Same-day: won't weight-bear + fever/unwell → septic arthritis (admit, aspirate, IV abx; Kocher); bone pain + pallor/bruising/lymphadenopathy/fever → very urgent FBC + paediatrics (NG12 leukaemia); suspected NAI → safeguarding. 🟠 Urgent ortho: SUFE (non-weight-bearing, frog-lateral X-ray), Perthes', DDH. 🟢 Routine: transient synovitis (exclusion; well child; rest/analgesia/safety-net/review). Don't over-label "growing pains".
SCA Quick Reference
The Limping Child — Consultation Playbook
Age · examine the hip · exclude septic/leukaemia · SUFE urgently
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🎯 The three pivots that pass this case
1 · Examine the hip
Knee/thigh pain in a child → examine the HIP (internal rotation). SUFE & Perthes' refer to the knee.
2 · Exclude the emergencies
Won't weight-bear + fever = septic arthritis (admit). Bone pain + systemic features = NG12 leukaemia (urgent FBC). Consider NAI.
3 · SUFE urgently, not physio
Overweight adolescent, ext. rotated leg, ↓ internal rotation → urgent orthopaedics + non-weight-bearing (avoid AVN).
⛔ Don't treat knee pain without examining the hip — you'll miss SUFE/Perthes' · Don't refer SUFE to physiotherapy or allow weight-bearing · Don't assume transient synovitis/"growing pains" in a febrile, unwell or non-weight-bearing child · Don't miss leukaemia (NG12) red flags or safeguarding · Reason by age