Limping Child

A limp is a presentation, not a diagnosis. It may come from pain, weakness, deformity, limb-length difference, neuromuscular control, inflammatory disease, infection, tumour, trauma or compensation. The safe clinician does not begin by reciting a long differential list. The safe clinician first asks: is this child sick, can they weight bear, is the limp painful, and what dangerous diagnosis must not be missed today?

Age is the strongest first organiser. Toddlers commonly present with occult trauma, infection, developmental hip issues, neuromuscular patterns or safeguarding concerns. School-age children raise the probability of transient synovitis, Perthes disease, infection, inflammatory disease and malignancy. Adolescents require a specific hip screen for slipped upper femoral epiphysis, even when the child points to the knee.

The hip deserves special attention because children localise pain poorly. Hip pathology may be felt in the thigh or knee. A teenager with knee pain and a normal knee examination may have SUFE. A younger child with a subtle limp and reduced hip abduction or internal rotation may have Perthes disease. A febrile non-weight-bearing child may have septic arthritis or osteomyelitis even if early radiographs are normal.

Observation is not a passive decision. Safe observation requires a well child, reassuring examination, improving symptoms, no red flags, a clear working diagnosis and explicit return triggers.

The gait pattern gives the first physiological clue. An antalgic gait shortens stance phase on the painful limb. Trendelenburg gait reflects hip abductor weakness, hip pain or altered femoral head mechanics. A short-leg gait suggests limb-length difference or pelvic obliquity. Circumduction, toe walking, spasticity, ataxia or foot drop move the differential toward neuromuscular disease.

The mechanism behind the limp differs by pathology:

• Septic arthritis raises intra-articular pressure and damages cartilage through inflammation and bacterial toxins.
• Transient synovitis causes a painful sterile effusion and should improve clinically.
• Osteomyelitis often starts in metaphyseal bone and may spread to soft tissue or adjacent joint.
• Perthes disease is femoral head osteonecrosis followed by fragmentation and remodelling.
• SUFE is failure through the proximal femoral physis; the epiphysis stays in the acetabulum while the metaphysis displaces.
• Toddler fracture causes tibial pain and reluctance to weight bear despite subtle initial radiographs.
• Malignancy may cause night pain, systemic symptoms or marrow pain before obvious radiographic change.
• Non-accidental injury may present as refusal to walk with an inconsistent or developmentally impossible mechanism.

History

The history should identify acuity, severity, red flags and the most likely anatomical source.

• Onset: sudden trauma, gradual limp, morning stiffness, intermittent limp, night pain or acute refusal to walk.
• Weight bearing: walking normally, limping, crawling, standing only with support, or complete refusal to weight bear.
• Systemic features: fever, malaise, weight loss, pallor, bruising, recurrent infections, recent viral illness or recent antibiotics.
• Pain location: hip, groin, thigh, knee, tibia, ankle, foot, back or abdomen. Do not accept knee pain as a knee diagnosis until the hip has been assessed.
• Trauma: mechanism, timing, witness account and whether the mechanism matches developmental ability.
• Background risks: previous hip disease, inflammatory disease, sickle cell disease, immunosuppression, malignancy, neuromuscular disease or safeguarding concerns.
• Course: improving, static, worsening, recurrent, activity-related or waking the child from sleep.

Examination

Observe before touching the child. A child who runs around the room is different from a child who lies still and refuses to move the hip. Note whether the gait is antalgic, Trendelenburg, short-leg, circumduction, toe-walking, spastic, ataxic or foot-drop pattern.

Examine from spine to foot:

1. General appearance, temperature, hydration, pallor, bruising and systemic illness.
2. Spine, abdomen and lymph nodes when symptoms are vague, systemic or poorly localised.
3. Hip range, especially internal rotation, abduction and pain with passive motion.
4. Knee examination, but do not stop there if the knee is normal.
5. Tibial, ankle and foot tenderness for toddler fracture, stress injury or foot pathology.
6. Neurological tone, reflexes, power, coordination and foot posture when the limp is painless or unusual.
7. Skin, bruising, swelling and injury patterns that raise safeguarding concern.

Pain with passive hip motion, especially in a febrile or non-weight-bearing child, is a high-risk finding. Loss of internal rotation in an adolescent suggests SUFE until excluded. Reduced abduction and internal rotation in a school-age child raises concern for Perthes disease.

Investigations should answer the dangerous question still open after history and examination. Do not order the same panel for every child without deciding what you are trying to exclude.

Radiographs

• AP pelvis and lateral hip views for hip, thigh or knee pain when Perthes disease or SUFE is possible.
• Tibia radiographs for toddler fracture; repeat imaging may show periosteal reaction if early films are normal.
• Local radiographs for focal bony tenderness or trauma.
• Skeletal survey through the appropriate safeguarding pathway when non-accidental injury is suspected.

Blood tests

FBC, ESR, CRP and blood cultures support infection risk assessment. They are particularly useful in febrile, non-weight-bearing or systemically unwell children. Normal early markers do not overrule a concerning examination.

Ultrasound

Hip ultrasound detects effusion but does not prove pus. It is most useful when interpreted with fever, weight-bearing status, pain with passive motion, inflammatory markers and clinical trajectory.

MRI

MRI is the escalation test when occult infection, abscess, tumour, stress fracture, discitis, early Perthes disease or unexplained persistent pain remains possible after initial assessment. MRI is also useful when symptoms are severe and the source is unclear.

If SUFE is possible, make the child non-weight bearing and obtain AP pelvis and appropriate lateral hip imaging. Do not force a painful frog lateral in a possible unstable slip.

• Transient synovitis: well child, recent viral illness, mild to moderate hip irritation and improving course.
• Septic arthritis: fever, toxic appearance, refusal to weight bear and painful passive motion.
• Osteomyelitis: focal metaphyseal tenderness, fever or pain out of proportion, sometimes with normal early radiographs.
• Perthes disease: school-age child with limp, hip stiffness and reduced abduction/internal rotation.
• SUFE: adolescent with hip, thigh or knee pain and obligatory external rotation.
• Toddler fracture: young child with tibial tenderness and reluctance to walk.
• Malignancy: night pain, systemic symptoms, bruising, pallor or persistent bone pain.
• Non-accidental injury: mechanism inconsistent with developmental ability or injury pattern.

Early

• Delayed septic arthritis diagnosis with cartilage injury.
• Missed SUFE with progression to unstable slip.
• Missed osteomyelitis with abscess formation.
• Inappropriate reassurance despite malignancy red flags.
• Unrecognised safeguarding concern.

Late

• Avascular necrosis or deformity from missed hip disease.
• Chronic osteomyelitis after delayed infection treatment.
• Growth disturbance from infection or physeal injury.
• Persistent gait abnormality due to missed neuromuscular or structural cause.
• Family loss of trust after vague safety-netting.

A limping child is a safety diagnosis until the dangerous causes are excluded. The first decision is not the final diagnosis; it is whether the child is systemically unwell, unable to weight bear, has severe pain, has a septic joint risk or has a non-orthopaedic emergency.

The assessment should use age bands. Toddlers commonly have occult trauma, toddler fracture or infection. Children aged four to eight need careful assessment for Perthes, transient synovitis and infection. Adolescents need slipped upper femoral epiphysis considered even when pain is felt in the knee. Any age can present with malignancy, inflammatory disease, discitis or non-accidental injury.

Transient synovitis is a diagnosis of recovery, not a label for every painful hip. A child who remains febrile, cannot weight bear, has rising inflammatory markers, severe passive-motion pain or persistent symptoms needs reassessment for septic arthritis, osteomyelitis, abscess or another diagnosis.

Do not start with a long list of diagnoses. Start with the child status: sick or well, weight bearing or not, painful or painless, and age band. This immediately separates septic arthritis and major red flags from the more common benign causes.

Transient synovitis is common, but the diagnosis should include why septic arthritis is unlikely. A well child who can weight bear, has mild symptoms after a viral illness, has improving pain and has reassuring inflammatory markers is very different from a febrile child who refuses to move the hip.

A normal X-ray is not the same as a normal child. Early osteomyelitis, tumour, toddler fracture, stress fracture and early Perthes disease can have subtle or normal radiographs. If the story remains concerning, escalate to MRI, repeat imaging or senior review rather than discharging on the basis of one normal film.

Non-accidental injury is not an accusation; it is a safety diagnosis that must be considered when the history, developmental stage and injury pattern do not match. The orthopaedic role is to recognise the mismatch, document carefully and activate the correct safeguarding pathway.

The discharge plan should sound precise: "This is the most likely diagnosis, these are the dangerous diagnoses we do not currently think are present, this is the follow-up plan, and these symptoms should bring you back urgently."

Common pitfalls

• Calling it transient synovitis before assessing septic arthritis risk.
• Forgetting that hip disease can present as knee pain.
• Relying on ultrasound effusion alone to diagnose septic arthritis.
• Missing SUFE because the child points to the knee.
• Ignoring night pain or systemic symptoms.
• Not considering safeguarding in a non-walking child with fracture.