Humerus, supracondylar fracture
Lateral :: XR - Plain Film || ACR Codes: 4.4 Single lateral radiograph of right elbow. Normally, the anterior fat pad is against the anterior surface of the distal humerus. Any joint effusion will displace this fat pad anteriorly giving it a 'sail' appearance, hence the term 'sail sign'. Also, in a normal elbow, the posterior fat pad is not visible in radiographs. In the setting of trauma in this case, the appearance of a posterior fat pad indicated an occult supracondlar fracture. The fat pads, however, may be abnormal in settings such as joint infection or inflammation. In this case, trauma was clearly the cause.