A rare case of posterior interosseous nerve palsy due to ganglion cyst arising from supinator muscle.

Here we present a rare case of ganglion cyst of the elbow joint arising from supinator muscle causing posterior interosseous nerve (PIN) palsy in a 40-year-old female who presented with weakness in finger extension and carrying out routine activities with right hand since 2 weeks. Patient had pain over the right forearm radiating to the right hand since 3 months. She also noted a swelling in the right forearm, which was gradually increasing in size since last 1 month. Atraumatic PIN compression is uncommon and is usually caused by compression of PIN in the arcade of Frohse, by radial recurrent artery, and fibrous band around the radiocapitellar joint. Reports of PIN palsy caused by ganglionic cyst in the elbow joint are rare and case reports regarding the same are sparingly reported. Here we report a case of PIN palsy secondary to ganglion cyst arising from supinator muscle, which recovered completely after excision of the ganglion cyst.