Painful limitation of the hip due to transient synovitis

Specialty: Pediatrics.

• Transient hip synovitis
• irritable hip
• transient infantile lameness

Why it occurs

• Transient synovitis of the hip (self-limited benign aseptic inflammation of the synovial membrane, very common between 3 and 8 years of age, frequently after a viral upper respiratory tract infection in the previous weeks)
• Septic arthritis of the hip (severe bacterial infection of the joint, commonly caused by Staphylococcus aureus or Kingella kingae, which constitutes a medical and surgical emergency)
• Legg-Calvé-Perthes disease (idiopathic avascular necrosis of the femoral head, typical in males aged 4 to 10 years, with a chronic course)
• Proximal femoral epiphysiolysis (displacement of the epiphysis on the femoral metaphysis, common in overweight adolescents, typically bilateral and subacute onset)
• Osteomyelitis of the proximal femur or pelvis (underlying bone infection that painfully limits the mobility of the limb)
• Juvenile idiopathic arthritis or post-streptococcal reactive synovitis.

Initial workup

Hip ultrasound (mandatory first-line test to confirm the presence of joint effusion in the coxofemoral joint and guide arthrocentesis if necessary). Simple AP and axial radiography of both hips (to rule out Perthes disease, occult fractures or epiphysiolysis). Blood analysis with complete blood count, ESR and CRP (essential for applying the Kocher predictive criteria for septic arthritis). Joint puncture with aspiration of synovial fluid under ultrasound control, with biochemical and cytological analysis, Gram stain and culture (reserved for well-founded 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.