title: Hip joint fluid in the presence of the vacuum phenomenon.
abstract: A 3-year old boy with an acute onset of hip pain and limitation of motion had 4 mm of crescent shaped intra-articular gas produced by manual traction radiography. Hip aspiration produced more than 2 ml of fluid from the hip. Manual traction radiography producing the vacuum phenomenon with release of crescent shaped intra-articular gas did not exclude joint fluid in this patient.
mesh_terms: D002675:Child, Preschool; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000473:pathology*; D006801:Humans; D008297:Male; D011859:Radiography; D013582:Synovial Fluid / Q000473:pathology*; D013585:Synovitis / Q000150:complications*; D014143:Traction