Diagnosis:
Elbow effusion
Discussion:
A. Normal lateral radiograph of the elbow. B. Plain film radiograph of the lateral
elbow which reveals the classic elbow fat pad sign. This is an invaluable soft tissue
finding in cases of intra-articular injury of the elbow. Fat is normally present within
the joint capsule of the elbow, but outside the synovium. Typically "hidden" in
the concavity of the olecranon and coronoid fossae, the fat is usually not visible on the
lateral radiograph. However, injuries that produce intra-articular hemorrhage cause
distension of the synovium and forces the fat out of the fossa, producing triangular
radiolucent shadows anterior and posterior to the distal end of the humerus. When present
in a patient with a history of acute trauma to the elbow, the fat pad sign indicates the
presence of an intra-articular hemorrhage, which in turn is often associated with an
intra-articular skeletal injury (usually the radial head in an adult).
AB
References:
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