A woman presented with left wrist pain. The patient was the restrained driver in a motor vehicle accident. On examination, there was tenderness along the ulnar aspect of the distal forearm. Radial pulses were palpable, and motor and sensory examinations were intact. Radiographs were obtained (figures 1 and 2). Pronator quadratus fat pad sign. The pronator quadratus muscle connects the anterior distal radius and ulna. A layer of fat separates the muscle from the flexor digitorum profundus muscles. Normally, this fat plane appears as a thin radiolucency immediately adjacent and parallel to the radius on radiographs. In patients with distal forearm fractures, blood may displace the fat plane anteriorly and create the pronator quadratus fat pad sign (figure 1). False-negatives occur if radiographs are poor quality or obtained before blood can accumulate, or if fractures are not under the pronator quadratus muscle. False-positives occur in some arthritides, infections and soft tissue injuries. Sensitivity and specificity of the sign are 26–65% and 70%, respectively. 2 Patients with a positive fat pad sign but otherwise normal radiographs may require additional imaging to assess for fracture. Our patient was found to have an ulna styloid fracture (figure 2). Non-displaced fractures of the distal forearm should be immobilised for 4–8 weeks.