The limping child
Fever and won't bear weight is septic arthritis until proven otherwise. Always examine the hip when a child has knee pain.
A 13-year-old overweight boy has had pain in his left knee for 3 weeks and now limps. His knee examination is normal. When you flex his left hip, it rolls outward, and internal rotation is reduced and painful.
A 5-year-old girl has been limping since yesterday after a cold last week. Temperature 37.6 °C, she will walk with a limp, and the right hip has mildly reduced movement.
Why is the boy's knee hurting, and how do you decide whether the girl's hip is septic?
- Fever, unwell, won't bear weightSeptic arthritis or osteomyelitis: bloods, ultrasound, orthopaedics today.
- Knee pain in a childAlways examine the hip.
- Think by age0–4, 4–10, and over 10 years have different causes.
- Bloods if any concernCBC, CRP, ESR, blood culture.
- ImagingAP and frog-leg lateral hips for SUFE, ultrasound for effusion.
- Transient synovitisWell, mild or no fever, after a cold: rest, NSAID, review in 24–48 hours.
- SafeguardingUnexplained fractures or injuries in young children.
- Fever and refusing to walk
- SUFE
- Night pain or weight loss
- Pallor or bruising
- Unexplained injury in a young child
- Limp lasting more than a week
- Septic arthritis
- Osteomyelitis
- SUFE presenting as knee pain
- Leukaemia
- Non-accidental injury
- Bone tumour
- Toddler's fracture
- Developmental dysplasia of the hip
| Kocher criteria | Non-weight-bearing, fever over 38.5 °C, ESR over 40 mm/h, WBC over 12,000/µL: more criteria = higher risk of septic hip |
| CRP | Above 20 mg/L is often added as a fifth predictor |
| Transient synovitis | Age 3–8, follows viral illness, settles within 1–2 weeks |
| Perthes disease | Age 4–8, avascular necrosis of the femoral head |
| SUFE | Age 10–16, often overweight, knee or hip pain: stop weight-bearing, orthopaedics urgently |
| Night pain, bruising, pallor | Think leukaemia or bone tumour |
Check every dose against a current drug reference and your hospital protocol.
On this page
History
- How long? Sudden or gradual? After injury?
- Fever, unwell, recent cold or diarrhoea.
- Will the child bear weight? Walk? Crawl?
- Night pain, weight loss, pallor, bruising: leukaemia or tumour.
- In young children: does the story fit? Delay? Other injuries?
- Knee pain: remember hip pain is often felt in the knee.
Examination
- Watch them walkAntalgic (short stance on the painful side), Trendelenburg, refusing to walk.
- LookSwelling, redness, bruising, rashes, leg length.
- FeelEach bone and joint from the spine to the feet; spine and abdomen too.
- MoveHip rotation (internal rotation lost early in hip disease), knee, ankle.
- GeneralTemperature, lymph nodes, liver and spleen, pallor, bruising.
Causes by age
Septic arthritis, osteomyelitis, toddler's fracture, DDH, non-accidental injury
Transient synovitis, Perthes disease, septic arthritis, juvenile arthritis
SUFE, Osgood-Schlatter, sports injury, bone tumour
Septic hip or transient synovitis?
| Feature | Transient synovitis | Septic arthritis |
|---|---|---|
| Age | 3–8 years | Any |
| Preceding illness | Viral, 1–2 weeks before | Sometimes |
| Fever | None or mild | High (over 38.5 °C) |
| Weight-bearing | Usually some | Refuses |
| Looks | Well | Unwell |
| ESR, CRP, WBC | Normal or mildly raised | High |
| Ultrasound | Small effusion | Effusion (needs aspiration) |
- Transient synovitis more likely
- rest, NSAID, review in 24–48 hours
- Ultrasound for effusion
- orthopaedics for aspiration
- treat as septic hip
See septic arthritis.
Specific conditions
| Condition | Clues | Management |
|---|---|---|
| Perthes disease | 4–8 years, boys, gradual limp, reduced hip movement | X-ray; orthopaedics |
| SUFE | 10–16, overweight, knee or hip pain, leg externally rotated | No weight-bearing; urgent orthopaedics (surgery) |
| Toddler's fracture | 1–3 years, after a minor fall, tender tibia | X-ray (may be normal at first); cast or boot |
| Osgood-Schlatter | Active adolescents, tender tibial tuberosity | Rest, ice, activity modification |
| Leukaemia | Bone pain, pallor, bruising, nodes, big liver or spleen | CBC and film urgently |
| DDH | Toddler, painless limp, leg length difference | X-ray or ultrasound, orthopaedics |
Investigations
| Test | When |
|---|---|
| CBC, CRP, ESR, blood culture | Fever or concern for infection |
| Blood film | Pallor, bruising, night pain |
| X-ray (AP and frog-leg lateral hips) | SUFE, Perthes, fractures |
| Ultrasound hip | Effusion |
| MRI | Osteomyelitis, early Perthes, unclear cases |
| Joint aspiration | Suspected septic arthritis |
Treatment
Common mistakes
- Examining only the knee in a child with knee pain.
- Calling SUFE a "sprain" and letting the child walk on it.
- Missing septic arthritis because the child was given ibuprofen and the fever settled.
- Not doing a CBC and film in a child with night pain and pallor.
- Missing non-accidental injury in a toddler.
Frequently asked questions
What causes a limp in a child?
Common causes include minor injury and transient synovitis. Serious ones include septic arthritis, osteomyelitis, Perthes disease, slipped upper femoral epiphysis, leukaemia and non-accidental injury.
Why examine the hip in a child with knee pain?
Hip problems such as SUFE and Perthes disease often cause pain referred to the knee.
What are the Kocher criteria?
Four predictors of septic hip in children: not bearing weight, fever above 38.5 °C, ESR above 40 mm/h and white cells above 12,000/µL. The more present, the higher the risk.
What is transient synovitis?
A short-lived inflammation of the hip after a viral illness in children aged about 3–8. The child is well and it settles within 1–2 weeks with rest and ibuprofen.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. An overweight 13-year-old has knee pain and a limp; the hip rolls outward on flexion. What is likely?
Answer: Slipped upper femoral epiphysis. SUFE: AP and frog-leg lateral hips, no weight-bearing, orthopaedics.
- Osgood-Schlatter disease: Knee tenderness, not hip signs.
- Transient synovitis: Younger, acute.
- Perthes disease: Younger.
- Growing pains: No.
2. A 5-year-old has a limp after a cold, is well, bears some weight and has a temperature of 37.6 °C. What is likely?
Answer: Transient synovitis. Rest, NSAID and review; return if fever or worse.
- Leukaemia: No other features.
- SUFE: Wrong age.
- Septic arthritis: Unlikely with these features.
- Fracture: No trauma.
3. A child with a limp has night pain, pallor and bruising. What must be excluded?
Answer: Leukaemia. Check a full blood count and film.
- Flat feet: No.
- Transient synovitis: No.
- Growing pains: Red flags present.
- Sprain: No.
4. A diabetic man has a chronic foot ulcer over the first metatarsal head; a sterile probe touches bone. What is the best imaging for osteomyelitis?
Answer: MRI of the foot. Diabetic foot osteomyelitis: positive probe-to-bone test, ulcer > 2 cm², raised ESR/CRP suggest it. MRI is the most accurate imaging (marrow oedema); X-ray changes lag 2–3 weeks. Bone biopsy (percutaneous/surgical) guides antibiotics; treat for ~6 weeks, debridement or minor amputation if needed. Offload pressure, revascularise ischaemic limbs, optimise glucose.
- Plain X-ray only: X-ray changes appear late.
- Ultrasound: Ultrasound does not assess bone.
- Bone scan as first test: Bone scan is less specific.
5. An obese 13-year-old boy has left knee pain and a limp for 4 weeks. On flexing the hip it rolls into external rotation. Klein’s line on the AP X-ray doesn’t intersect the femoral epiphysis. What is the treatment?
Answer: In situ pinning. Slipped upper (capital) femoral epiphysis: adolescents (10–15), obese, boys; hormonal (hypothyroidism, renal osteodystrophy). Knee pain referred from the hip, limp, obligatory external rotation on flexion; frog-leg lateral X-ray shows the slip; Klein’s line fails to intersect the epiphysis. Treat urgently with in situ screw fixation (no forceful reduction — AVN). Consider the other hip (bilateral in 20–40%).
- Forceful closed reduction: Forceful reduction risks avascular necrosis.
- Physiotherapy only: Physiotherapy alone lets the slip progress.
- Total hip replacement: Hip replacement is not for adolescents.
6. After a displaced intracapsular fracture of the femoral neck, the femoral head is at risk of avascular necrosis. Which artery is its main blood supply?
Answer: Medial circumflex femoral artery. Retinacular branches of the medial circumflex femoral artery run up the neck within the capsule to supply most of the femoral head. Displaced intracapsular fractures tear them, causing avascular necrosis; such fractures are usually treated by hemiarthroplasty in older patients. The artery of ligamentum teres is significant mainly in children.
- Lateral circumflex femoral artery: Contributes less, mainly to the anterior neck.
- Artery of the ligamentum teres (obturator): Important in children; minor in adults.
- Superior gluteal artery: Supplies the gluteal muscles.
- Femoral artery directly: Gives the circumflex arteries via the profunda.
7. What is the most common cause of acute haematogenous osteomyelitis in all age groups, and which organism is particularly linked to sickle cell disease?
Answer: S. aureus; Salmonella in sickle. S. aureus is the commonest cause overall. Salmonella is classically associated with sickle cell disease (infarcted bone, gut organisms), though S. aureus still occurs. Pseudomonas: puncture through trainers, IV drug users. TB: spine (Pott's disease). Children: metaphysis of long bones. Neonates: group B strep, E. coli.
- S. pyogenes; E. coli: Not the commonest.
- M. tuberculosis; Pseudomonas: TB affects the spine; Pseudomonas after foot punctures.
- Haemophilus; S. epidermidis: Not the commonest.
- Pseudomonas; Salmonella: Pseudomonas is not commonest.
References and dose sources
- BOA/BSCOS guidance
- NICE NG12 — suspected cancer
- NICE CG89 — child maltreatment
- BOAST — management of children with acute musculoskeletal infection
- NICE CKS — acute childhood limp
- Ibuprofen dosing: Drugs.com: Ibuprofen dosage (see also our ibuprofen dose page)
- Paracetamol dosing: Drugs.com: Acetaminophen (paracetamol) dosage (see also our paracetamol dose page)
- Ceftriaxone dosing: Drugs.com: Ceftriaxone dosage (see also our ceftriaxone dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.