What do I do if a child is not walking due to lower limb pain?

Immediate Evaluation of a Non-Ambulatory Child with Lower Limb Pain

Obtain focused radiographs of the tibia/fibula immediately, as these are the most common sites of occult fractures in young children who refuse to walk, and assess for fever, inflammatory markers, and joint effusion to rule out septic arthritis—a medical emergency requiring urgent intervention. 1, 2

Critical Red Flags Requiring Urgent Action

• Fever >101.3°F (38.5°C) combined with refusal to bear weight strongly suggests septic arthritis and requires urgent ultrasound of the hip to assess for effusion 2, 3
• If fever is present with elevated inflammatory markers (ESR >40 mm/hr, WBC >12,000/mm³, or CRP >20 mg/L), perform ultrasound-guided joint aspiration for cell count, Gram stain, and culture 2, 3
• Septic arthritis requires rapid diagnosis within hours to prevent permanent joint damage and significant morbidity 2

Systematic Diagnostic Approach

History Elements to Obtain

• Timing and pattern: When pain started, duration of each episode, whether intermittent or constant 1
• Trauma history: Any recent falls, injuries, or unusual activities 2
• Associated symptoms: Fever, systemic illness, recent infections 1, 3
• Pain localization: Remember that young children cannot accurately localize pain—hip pathology commonly presents as knee or thigh pain 1, 2

Physical Examination Priorities

• Observe gait if the child will attempt walking 1
• Assess for the "three As" in children: anxiety, agitation, and analgesic requirement—these may indicate serious pathology when verbal communication is limited 4
• Palpate systematically: Check for swelling, redness, deformity, and tenderness along bones and joints 1
• Neurological assessment: Evaluate muscle strength, reflexes, and sensation 1

Initial Imaging and Laboratory Strategy

First-Line Imaging

• Plain radiographs of tibia/fibula bilaterally are the initial imaging of choice, as toddler's fractures (spiral tibial fractures) are common and may be subtle 1, 2
• If no focal findings on exam, obtain radiographs of both lower extremities rather than just the painful area 1, 3

Laboratory Testing (When Indicated)

• Order CBC, ESR, and CRP if infectious or inflammatory process is suspected based on fever or systemic symptoms 1, 3
• These tests help stratify risk for septic arthritis when combined with clinical findings 3

Advanced Imaging

• Ultrasound of the hip is particularly useful for detecting joint effusions and guiding aspiration 2
• MRI should be considered if initial radiographs are normal, symptoms persist, and osteomyelitis or occult fracture is suspected 1, 2

Key Differential Diagnoses by Priority

Emergent Conditions

• Septic arthritis: Medical emergency requiring intervention within hours 2, 3
• Osteomyelitis: Often associated with septic arthritis, may require MRI for diagnosis 2

Common Traumatic Causes

• Toddler's fracture (spiral tibial fracture): Most common occult fracture in young children 1, 2
• Stress fractures and soft tissue injuries 1

Other Important Diagnoses

• Transient synovitis: Most common overall diagnosis in limping children 3
• Legg-Calvé-Perthes disease and slipped capital femoral epiphysis in appropriate age groups 2

Management Based on Initial Findings

If Normal Radiographs with Improving Symptoms

• Observation and reassurance with follow-up in 1-2 weeks if symptoms persist 1
• Provide analgesia (short-course NSAIDs are appropriate) 4

If Normal Radiographs with Persistent Symptoms

• Repeat clinical examination and consider follow-up radiographs, as approximately 10% of tibial fractures are only visible on repeat imaging 1, 2
• Consider advanced imaging (MRI or ultrasound) 1

If Fracture or Joint Abnormality Identified

• Orthopedic consultation is required 1

If Infection Suspected

• Infectious disease consultation and urgent intervention 1

Critical Pitfalls to Avoid

• Never assume normal radiographs rule out fracture—10% of tibial fractures appear only on follow-up films 1, 2
• Do not focus only on the site of reported pain—young children mislocalize pain frequently, and hip pathology presents as knee pain in up to 30% of cases 1, 2
• Do not miss infection signs—fever and elevated inflammatory markers require urgent evaluation for septic arthritis 2, 3
• Ensure adequate follow-up—serious conditions like spinal discitis have been missed on initial evaluation 1
• Consider acute compartment syndrome in children with trauma, especially if the child shows anxiety, agitation, and high analgesic requirements despite treatment 4