Computed tomography and ultrasonography for diagnosis of hip joint effusion in children.

Nineteen consecutive children with transient synovitis of the hip were examined for intracapsular joint effusion using computed tomography (CT) and ultrasonography (US). The two techniques were highly correlated in measurements of the anterior displacement of the joint capsule, indicating both to be reliable diagnostic tools. Such an effusion is clinically important because of the increase in intracapsular pressure with ensuing disturbance in the vascular supply to the proximal femoral epiphysis, as demonstrated experimentally and clinically in transient synovitis.