What elbow imaging sign suggests an occult fracture?

• A. Posterior fat pad sign
• B. Anterior fat pad sign
• C. Normal X-ray
• D. Joint effusion

Answer: (A)

A posterior fat pad sign on a lateral elbow X-ray is the clearest clue that an occult fracture is present. The elbow’s fat pads sit hidden within the joint capsule, but when there is intra-articular fluid from a fracture (bleeding or inflammation), the posterior pad is pushed into view, creating the sail-like posterior fat pad appearance. This radiographic sign signals joint effusion due to a fracture even when the fracture line itself isn’t visible on the X-ray. The anterior fat pad sign can also indicate effusion, but the posterior sign is the classic and more specific indicator of an occult elbow fracture.