What is the appropriate management for a child presenting with bilateral knee pain at night?

Bilateral Knee Pain at Night in a Child

This child requires immediate evaluation to exclude serious pathology—particularly infection, neoplasm, or inflammatory disease—as nighttime pain is a critical red flag that demands urgent workup. 1

Why Night Pain is a Red Flag

Night pain in children is a hallmark symptom of serious underlying pathology and should never be dismissed as benign "growing pains" without proper evaluation:

• Spine neoplasms present with persistent nighttime back pain in 25-30% of affected children, and this symptom pattern applies to other musculoskeletal tumors as well 1
• Infection (osteomyelitis, discitis, septic arthritis) characteristically causes persistent nighttime pain that is refractory to rest 1
• Inflammatory conditions such as juvenile idiopathic arthritis commonly manifest with night pain 1
• Night pain or pain at rest is characteristic of infection, whereas pain only with weight-bearing suggests mechanical issues 1

Critical Initial Assessment

Immediate Clinical Evaluation Must Include:

• Fever, inability to bear weight, refusal to move joints, systemic toxicity to assess for septic arthritis—an orthopedic emergency that can rapidly destroy cartilage 2
• Hip examination is mandatory even when the child complains of knee pain, as hip pathology (transient synovitis, septic arthritis, Legg-Calvé-Perthes disease, slipped capital femoral epiphysis) commonly presents as referred knee pain 2, 3, 4
• Spine examination must be performed, as lumbar pathology can present as bilateral lower extremity pain 3
• Duration of symptoms >4 weeks is another red flag requiring imaging 1

Laboratory Testing:

• ESR, CRP, and complete blood count should be obtained immediately 1, 2
• ESR ≥40 mm/hour, WBC ≥12,000 cells/mm³, and CRP >2.0 mg/dL are predictive of septic arthritis 2
• Leukocytosis, elevated ESR, and elevated CRP suggest infection or inflammatory disease 1

Imaging Algorithm

Initial Imaging:

• Plain radiographs of both knees (AP and lateral views) are the first imaging study 2, 5
• Simultaneously obtain hip radiographs given the high likelihood of referred pain from hip pathology 2, 3
• Radiographs can identify fractures, osteomyelitis changes, or alternative diagnoses and are safe and inexpensive 2

If Radiographs Are Normal But Red Flags Present:

• MRI of the complete spine without IV contrast is rated 8/9 (usually appropriate) when night pain is present with negative radiographs 1
• MRI with and without IV contrast is rated 6/9 (may be appropriate) and is specifically useful when there is concern for inflammation, infection, or neoplasm 1
• Ultrasound of affected joints is the next step if infection is suspected, to identify joint effusions and guide arthrocentesis 2

Most Likely Serious Diagnoses to Exclude

Infection:

• Septic arthritis requires immediate orthopedic consultation for arthrotomy, irrigation, and debridement 2
• IV antibiotics targeting Staphylococcus aureus (most common pathogen) must be started if septic arthritis is confirmed 2
• Osteomyelitis requires IV antibiotics followed by prolonged oral course 2

Neoplasm:

• Persistent nighttime pain refractory to conservative management is present in 25-30% of children with spinal neoplasm, and similar patterns occur with other bone tumors 1
• Benign tumors include osteochondroma, osteoblastoma, osteoid osteoma, giant cell tumor, and aneurysmal bone cyst 1
• Malignant tumors include leukemia, lymphoma, and rarely metastasis 1

Inflammatory Disease:

• Juvenile idiopathic arthritis commonly presents in late childhood and can affect multiple joints bilaterally 1

Common Pitfall to Avoid

Do not attribute bilateral knee pain at night to "growing pains" without proper workup. Growing pains typically:

• Occur in younger children (not adolescents) 6
• Are localized to thighs, shins, or calves 6
• Are relieved by massage 6
• Occur in otherwise healthy children with normal growth and development 6

Bilateral presentation does NOT exclude serious pathology—infection, neoplasm, and inflammatory conditions can all present bilaterally 1, 6

Management Based on Findings

• If septic arthritis confirmed: Immediate orthopedic consultation and IV antibiotics 2
• If osteomyelitis confirmed: IV antibiotics followed by prolonged oral course 2
• If neoplasm suspected: Urgent oncology referral and advanced imaging 1
• If inflammatory arthritis suspected: Rheumatology referral and consideration of disease-modifying therapy 1
• Only if all serious pathology excluded: Consider benign diagnoses like joint hypermobility syndrome or fibromyalgia, which can present with bilateral pain but should be diagnoses of exclusion 6