Patient fell on an outstretched elbow.
Ultrasound showed a subtle fracture of the radial head. A haemarthrosis was present.
It is important always to ultrasound the interosseous membrane, best seen from the dorsal aspect.
This ultrasound showed a torn interosseous membrane. With slight compression on the dorsal aspect, the muscles were seen to bulge through the torn membrane. The right side was normal.