Snapshot A 7-year-old boy presents with 1 week of subjective low grade fevers and sudden onset right hip pain. His parents noticed a new limp in the past few days. They also report that the patient had a recent upper respiratory infection about 2 weeks ago. Physical exam reveals a crying but otherwise well-appearing child. He has a temperature of 100.0°F (37.8°C). There is limited range of motion of the right hip. Introduction Clinical definition benign transient synovitis of the hip, often characterized by acute hip pain Epidemiology Demographics male > female children 3-8 years of age this is the most common cause of acute hip pain in this age group uncommon in adults Risk factors preceding viral infection Etiology Pathogenesis sterile synovial inflammation and joint effusion Presentation Symptoms acute-onset limp or refusal to bear weight acute hip or groin pain Physical exam well-appearing child limping on the affected side may have limited range of motion of the hip due to effusion may have tenderness to palpation Imaging Radiography indication only indicated if there is suspicion for other hip pathology, such as Legg-Calve-Perthes disease recommend views anteroposterior pelvis lateral views of both hips findings normal findings or joint space widening Studies Making the diagnosis most cases are clinically diagnosed Differential Septic arthritis distinguishing factors the child is typically ill-appearing and febrile elevated white blood cell count Legg-Calve-Perthes disease distinguishing factors physical exam often reveals atrophy in the thighs and leg asymmetry radiography shows sclerosis in the femoral head Treatment Conservative rest and observation indication for all patients Medical nonsteroidal anti-inflammatory drugs indication pain management Complications None Prognosis Typically resolves within 1 week