Limp in Children

Limp is an abnormal, asymmetric gait pattern and a common presenting complaint across childhood. The differential diagnosis is extremely broad, spanning benign, self-limiting conditions through to serious, time-critical pathology requiring urgent recognition and treatment.

The clinical approach centres on a structured, age-stratified differential diagnosis, because likely causes differ substantially between age groups. It also requires careful, systematic assessment for red flag features that warrant urgent further evaluation.

Age-stratified differential diagnosis

• In toddlers and young children (generally one to three years), the commonest cause of acute limp is transient synovitis.
• Septic arthritis is the critical, time-sensitive diagnosis that must always be actively considered and excluded.
• Developmental dysplasia of the hip presents later than the neonatal period where it has not been previously identified and treated.
• Occult fracture includes the classic "toddler's fracture," a subtle, spiral fracture of the tibia occurring with relatively minor trauma, sometimes unwitnessed.
• Less commonly there is an underlying malignancy, including leukaemia, which can present with bone pain and limp reflecting marrow infiltration.
• In children aged four to ten years, important causes include transient synovitis and septic arthritis, both with declining relative frequency compared with the youngest age group.
• Legg-Calvé-Perthes disease peaks in incidence in this age range, as does juvenile idiopathic arthritis.
• In older children and adolescents (generally ten years and older), slipped capital femoral epiphysis peaks in incidence. It is particularly relevant with rapid growth and obesity, and is a critical diagnosis requiring prompt recognition.
• Juvenile idiopathic arthritis, overuse musculoskeletal injury and, less commonly, malignancy remain relevant.
• Referred pain is an important principle across all age groups. Hip pathology frequently presents with referred pain to the knee, reflecting shared innervation via the obturator nerve.
• Any child presenting with knee pain therefore warrants careful examination of the hip.

• A detailed history is the essential foundation of assessment. It covers the onset (acute versus gradual), duration, and any preceding trauma or intercurrent illness.
• A preceding viral upper respiratory tract infection is relevant, given its common association with transient synovitis.
• Ask about associated systemic symptoms (fever, weight loss, or night sweats), which raise concern for infection or malignancy.
• Full examination includes careful observation of gait pattern and assessment of the entire lower limb. The site of pathology may not correspond to the site of pain, particularly with the referred hip-to-knee pain pattern.
• Also assess range of motion at each relevant joint, and palpate carefully for localised tenderness, swelling or warmth.
• Red flag features warrant urgent further evaluation: inability to bear weight, fever and systemic upset (raising concern for septic arthritis or osteomyelitis), and significant, disproportionate pain.
• Night pain or pain waking the child from sleep raises concern for malignancy, as does any associated weight loss or other systemic symptom.
• Any red flag feature warrants prompt, urgent evaluation rather than reassurance and observation alone.
• A limping child under three years of age warrants particular caution. This age group is less able to communicate the location and character of pain reliably.
• Serious underlying pathology, including septic arthritis and occult fracture, is also relatively more common in this younger age group than in older children.

• Full clinical assessment is the foundation of diagnostic evaluation. It combines the age-stratified differential diagnosis with careful, systematic screening for red flag features.
• Where fever, significant pain or inability to bear weight makes septic arthritis or another significant infection a concern, pursue urgent investigation without delay.
• This includes full blood count, inflammatory markers and blood cultures, together with joint aspiration where clinically indicated, following the diagnostic principles for septic arthritis and transient synovitis.
• Plain radiography of the affected limb is the appropriate, standard initial imaging. Include the hip in any child presenting with knee pain, given the referred pain pattern.
• Radiography supports identification of a fracture, Legg-Calvé-Perthes disease, or slipped capital femoral epiphysis where relevant to the presentation and age.
• Further, more specific investigation is directed by the clinical presentation and initial findings, following the diagnostic principles for the relevant individual conditions. Options include ultrasound, which is particularly valuable for identifying a hip joint effusion, magnetic resonance imaging, or bone scan.

• Management is directed entirely by the underlying cause identified through the structured diagnostic approach. It follows the principles for transient synovitis, septic arthritis, developmental dysplasia of the hip, Legg-Calvé-Perthes disease, slipped capital femoral epiphysis, and juvenile idiopathic arthritis.
• Any child with a suspected or confirmed red flag feature, particularly inability to bear weight combined with fever or significant systemic upset, warrants urgent assessment.
• Where septic arthritis remains a genuine concern after initial evaluation, arrange urgent orthopaedic referral and, where indicated, prompt joint aspiration.
• This diagnosis is time-critical, and significant delay carries a substantial risk of joint destruction.
• Where initial assessment is reassuring and no red flag feature is present, structured observation with clear, explicit safety-netting advice is appropriate for many presentations. Safety-netting should name the features that would warrant urgent reassessment.
• This is particularly relevant where transient synovitis is the most likely diagnosis.
• Clear communication with the family underpins safe, effective management of this common, though diagnostically broad and occasionally time-critical, paediatric presenting complaint. It covers the working diagnosis, the plan for any further investigation or follow up, and safety-netting advice on red flag features.