1. The anterior fat pad of the elbow can be visualized normally as a thin radiolucent line just anterior to the coranoid fossa (anterior border of the distal humerus). However, when the elbow joint becomes distended (i.e.,hemarthrosis secondary to fracture within the joint space), the anterior fat pad is displaced further anteriorly and superiorly to form an anterior "Sail Sign," or more prominent lucency.
  2. The posterior fat pad lies over the olecranon fossa and normally is not visible because the olecranon fossa is much deeper (more concave) than the coranoid fossa. Visualization of the posterior fat pad (even as only a thin radiolucentline on the lateral view) indicates marked distention of the joint capsule, due to hemarthrosis from an intra-articular fracture and is therefore always pathologic.
  3. The anterior humeral line is drawn along the anterior surface of the distal humeruson a true lateral. Normally this line should intersect the middle third of the capitellum. If there is a supracondylar fracture with posterior displacement of the distal segment, the anterior line will either intersect the anterior third of the capitellum or does not intersect the capitellum at all.
  4. The radiocapitellarline is drawn along the central axis of the radius on the lateral view. Normally, this line should intersect the center of the capitellum (in all views). If the line does not transect the middle of the capitellum, either the radial head is dislocated or there is a fracture through the radial neck region.

On this true lateral:

  1. There are both an anterior and posterior fat pads.
  2. The anterior humeral line intersects the anterior third of the capitellum rather than the middle third.