SFMS Radiology Practice Test

When checking elbow radiographs, fractures can be subtle, so radiologists look for indirect signs of joint injury. The most telling clue is the fat pad sign, especially the posterior fat pad sign. Inside the elbow there are fat pads that are normally hidden on X-ray, but when a fracture bleeds into the joint, inflammatory fluid pushes these pads outward. On a lateral view, this appears as a visible posterior fat pad behind the olecranon, giving a sail-like appearance. This elevation of the fat pads indicates intra-articular injury and strongly suggests a fracture, even if the fracture line itself isn’t seen. In contrast, a sprain is a soft-tissue injury not typically visible on X-rays; a dislocation would show obvious misalignment rather than just fat pad elevation; and soft tissue edema without fracture is non-specific. Therefore, seeing elevated fat pads on an elbow radiograph is the best radiographic support for a fracture.