Flexor Digitorum Profundus (FDP) Avulsion (Jersey Finger; Rugby Finger; Sweater Finger) By Paul L Liebert, MD, Tomah Memorial Hospital, Tomah, WI Reviewed / Revised Oct 2021 | Modified Nov 2021 View Patient Education Etiology Symptoms and Signs Diagnosis Treatment Key Points Flexor digitorum profundus avulsion generally occurs at the tendon's insertion at the distal phalanx.