Painful limitation of the coxofemoral joint with acute lameness

Specialty: Pediatrics.

• Transient hip synovitis
• referred irritable hip pain
• painful hip limitation

Why it occurs

• Transient synovitis of the hip or irritable hip (self-limited benign aseptic inflammation of the synovial membrane, very common in male children aged 3 to 8 years, frequently preceded by a viral upper respiratory tract infection in the previous weeks)
• Septic arthritis of the hip (suppurative bacterial infection of the joint, commonly caused by Staphylococcus aureus, Streptococcus pyogenes or Kingella kingae, which constitutes a medical and surgical emergency requiring immediate drainage)
• Legg-Calvé-Perthes disease (idiopathic avascular necrosis of the femoral head, which associates limitation of coxofemoral mobility and subacute-chronic lameness)
• Proximal femoral epiphysiolysis or slipped femoral epiphysis (displacement of the femoral epiphysis on the metaphysis, common in overweight male adolescents)
• Osteomyelitis of the proximal femur or iliac bones of the pelvis
• Juvenile idiopathic arthritis or osteoid osteoma of the femoral neck.

Initial workup

Bilateral hip ultrasound (mandatory first-line test to confirm the presence of joint effusion in the coxofemoral joint and guide diagnostic/evacuative arthrocentesis if infection is suspected). Plain AP pelvis x-ray in frog position (Lauenstein) to rule out Perthes disease, stress fractures, osteomyelitis or epiphysiolysis. Blood analysis with complete blood count, ESR and CRP (essential for the application of the Kocher criteria for septic arthritis). Joint puncture (arthrocentesis) under ultrasound guidance with cytological, biochemical study, Gram stain, bacterial PCR and synovial fluid culture if there are criteria for suspicion of septic arthritis.

Standard management

• Relative rest in unloading of the joint is the most effective therapeutic measure for transient synovitis. Ibuprofen — first choice non-steroidal anti-inflammatory for its excellent joint penetration and pain control; dose of 10 mg/kg orally every 6-8 hours for 5 to 7 days, administered with food
• Paracetamol — analgesic alternative; dose of 15 mg/kg orally every 4-6 hours
• Intravenous cloxacillin or cefazolin (indicated urgently only in confirmed or highly suspected septic arthritis; cloxacillin dose of 100-150 mg/kg/day IV divided every 6 hours). Do not use oral corticosteroids routinely.