A Case of Antalgic Gait in the Pediatric Population: Transient Synovitis vs. Osteomyelitis

Introduction/Background:

An 18-month-old male presented to clinic with limp for 1 week. Patient was recovering from a cold with resolved rhinorrhea and was treated with NSAIDs every 6 hours with minimal improvement in ambulation. In the clinic, the patient was very irritable with limited use of left leg. Mother denied any recent falls/trauma, fevers, joint swelling, rashes, changes in behavior, cough, congestion. Reported Father was at home sick with diagnosed strep throat. Due to non-improving symptoms, the patient was transferred to ED for further workup and admitted to the floor in stable condition.

Description:

Initial exam in the ED: Afebrile with stable vitals. No swelling, erythema, or warmth noted on b/l hip, knee, and ankle joints. No tenderness to palpation over hip, femur, knee, leg or ankle. Pain with passive range of motion (PROM) of left hip and knee. No pain with PROM of ankles. Sporadically moved left lower extremity. 5/5 strength. 2+ dorsalis pedis pulse. Throughout exam the patient was grimacing in pain. On ambulation, patient favored the right leg and upon bearing weight with left leg, patient immediately buckled. No neurological symptoms or signs. Initial XR imaging was all negative, but after persistence of fevers, an MRI was obtained. Final diagnosis was osteomyelitis with intraosseous abscess of the distal left femur. Upon discovery of osteomyelitis on MRI, blood cultures x2 were taken and patient was started on Cefazolin 50mg/kg IV q8h and transitioned to Cephalexin 50 mg/kg/dose PO TID for 6 weeks on discharge. Orthopedic surgery performed irrigation and excisional debridement of osteomyelitis, left distal femur. Bone biopsy sent out for culture. Safe ambulation and mobility education left leg strengthening and gentle knee PROM. No physical activity restrictions. Patient was safe for discharge home from a mobility standpoint, no assisted device or further physical therapy needed.

Discussion:

Differentiating septic arthritis from transient synovitis in children with an irritable hip is crucial but challenging due to overlapping symptoms. The Kocher criteria, though commonly used, have shown limited reliability for the knee. Persistent symptoms despite NSAID therapy, normal imaging, and elevated inflammatory markers (ESR, CRP) should raise suspicion for a more serious condition like septic arthritis or osteomyelitis.