What is the recommended evaluation and management for leg pain in children, including identification of red‑flag signs and appropriate treatment?

Leg Pain in Children: Evaluation and Management

Begin with immediate assessment for red-flag signs requiring urgent intervention, as septic arthritis can cause permanent joint damage within hours if not diagnosed and treated emergently. 1, 2

Critical Red Flags Requiring Urgent Evaluation

• Fever >101.3°F (38.5°C) with refusal to bear weight strongly suggests septic arthritis and requires urgent hip ultrasound to assess for effusion 1, 2
• Elevated inflammatory markers (ESR >40 mm/hr, CRP >20 mg/L, WBC >12,000/mm³) necessitate ultrasound-guided joint aspiration for cell count, Gram stain, and culture 1, 2, 3
• The "three As"—anxiety, agitation, and high analgesic requirement—may indicate serious pathology including compartment syndrome or infection when verbal communication is limited 1
• Night pain, fever, unintentional weight loss, or pain lasting >4 weeks suggest infection, inflammation, or malignancy requiring advanced imaging 4, 5
• Inability to bear weight is associated with bacterial infection including osteomyelitis, septic arthritis, or intramuscular abscess 3

Essential History Elements

• Obtain specific timing and pain pattern details, as young children frequently mislocalize pain—hip pathology presents as thigh or knee pain in up to 30% of cases 1
• Document trauma history carefully, as even minor falls can cause occult fractures 1
• Assess for systemic symptoms including fever, night sweats, weight loss, and anorexia, which suggest infection, inflammation, or malignancy 5
• Determine pain characteristics: recurrent pain lasting >3 months without systemic symptoms, localizing signs, joint involvement, limp, or activity limitation suggests benign growing pains 6

Physical Examination Priorities

• Observe gait if ambulatory and palpate systematically along the entire lower extremity to assess for swelling, redness, deformity, and focal tenderness 1, 5
• Examine range of motion of individual joints to localize pathology 5
• Perform neurological assessment including deep tendon reflexes and muscle tone 1
• Assess for non-musculoskeletal causes, as conditions outside the musculoskeletal system can cause limping 5
• Evaluate for signs of serious pathology: anxiety, agitation, and high analgesic requirements 1

Initial Diagnostic Workup

Imaging Algorithm

• First-line imaging: plain radiographs of bilateral tibia/fibula and hip/pelvis, as occult fractures are the most common cause of leg pain and hip pathology frequently refers to the thigh 1, 2
• Approximately 10% of tibial fractures appear only on follow-up radiographs, so normal initial films do not exclude fracture 1
• MRI without contrast is indicated when red flags are present with negative radiographs, particularly for detecting osteomyelitis, soft tissue pathology, or stress injuries 4, 3
• Ultrasound is valuable for detecting joint effusions and soft tissue evaluation, with the advantage of dynamic assessment and contralateral comparison 1

Laboratory Testing

• Laboratory tests are NOT necessary for diagnosis of growing pains when precise inclusion criteria are met: recurrent pain >3 months without systemic symptoms, localizing signs, joint involvement, limp, or activity limitation 6
• When red flags are present, obtain CBC, ESR, CRP to evaluate for infection or inflammation 2, 3
• ESR >36 mm/hr and CRP >60 mg/L are found in children with osteomyelitis or septic arthritis 3
• Assess electrolytes including calcium and magnesium if cramping is prominent, as hypocalcemia and hypomagnesemia can cause muscle cramping 7

Differential Diagnosis by Priority

Emergent Conditions

• Septic arthritis is a medical emergency requiring diagnosis within hours to prevent permanent joint damage 1, 2
• Osteomyelitis often requires MRI for diagnosis and should be considered with fever, inability to bear weight, and elevated inflammatory markers 1, 3

Common Acute Causes

• Toddler's fracture (spiral tibial fracture) is the most common occult fracture in young children 1
• Transient synovitis is the most common diagnosis overall in limping children 2
• Trauma-related injuries including contusions, foreign body in foot, and fractures 2

Referred Pain

• Hip pathology (Legg-Calvé-Perthes disease, slipped capital femoral epiphysis, transient synovitis) can present as referred thigh or knee pain in 30% of cases 1

Chronic/Benign Causes

• Growing pains are common non-specific lower leg/foot pains, often associated with pes planovalgus, and are a clinical diagnosis requiring no laboratory testing when classic criteria are met 7, 6
• Restless Legs Syndrome is characterized by urge to move legs with uncomfortable sensations that worsen during rest and improve with movement 7

Management Algorithm

If Red Flags Present (Fever, Inability to Bear Weight, Elevated Inflammatory Markers)

• Urgent hip ultrasound to assess for effusion 1
• Ultrasound-guided aspiration if effusion is present for cell count, Gram stain, and culture 1
• Immediate orthopedic or infectious disease consultation for suspected septic arthritis 2

If Normal Radiographs with Improving Symptoms

• Observation and reassurance 1
• Short-course NSAIDs for analgesia (see pain management section below) 1
• Follow-up in 1-2 weeks 1

If Normal Radiographs with Persistent Symptoms

• Repeat clinical examination 1
• Consider follow-up radiographs in 7-10 days, as 10% of fractures only appear on repeat imaging 1
• Advanced imaging (MRI or ultrasound) if symptoms worsen or red flags develop 1, 3

If Classic Growing Pains (Recurrent >3 Months, No Red Flags)

• No laboratory testing or imaging required when precise inclusion criteria are met 6
• Reassurance and supportive care 6
• Orthotic support may benefit children with pes planovalgus 7

Pain Management

Pharmacological Interventions

• Acetaminophen and NSAIDs are appropriate for mild to moderate pain 4
• Oral opiates are appropriate for moderate pain if no contraindications to oral medications exist 4
• Small titrated doses of IV opiates can be used for severe pain without affecting clinical examination or neurologic assessments 4
• Combination therapy with acetaminophen enhances NSAID effect 4
• Pain medication should be provided around-the-clock for anyone in whom moderate pain is anticipated 4

Non-Pharmacological Interventions

• Cognitive behavioral strategies, distraction, and breathing interventions are very effective in reducing pain and improving compliance 4
• Parents function as "coaches" for cognitive behavioral strategies, providing encouragement for coping mechanisms 4
• Massage, heat compresses, ice packs, and repositioning should be considered as adjuncts 4
• Audio-visual entertainment is highly effective in distracting children and reducing anxiety 4

Pain Assessment

• Use age-appropriate validated pain scales: PIPP-R for neonates, COMFORT-B scale or FLACC scale for infants and children 4
• Reassess pain within 30-120 minutes after intervention depending on medication half-life 4

Critical Pitfalls to Avoid

• Never assume normal radiographs exclude fracture, as 10% of tibial fractures only appear on follow-up films 1
• Never focus only on the reported pain site, as young children mislocalize pain and hip pathology presents as thigh/knee pain in 30% of cases 1
• Never delay evaluation of fever with inability to bear weight, as septic arthritis causes permanent damage within hours 1, 2
• Never ignore the "three As" (anxiety, agitation, analgesic requirements), as these suggest serious pathology 1
• Never assume pain management masks symptoms or clouds mental status—pain medications make children more comfortable and facilitate examination, aiding in diagnosis 4
• Never undertreat pain in children—proactive use of appropriate analgesic therapy is essential 4
• Never order laboratory tests for classic growing pains when precise inclusion and exclusion criteria are met on history and physical examination 6