Pain dysfunction syndrome of the knee.

Pain dysfunction syndrome is a descriptive term recommended by Amadio to describe patients whose pain is excessive, nonanatomic, and out of proportion to their injury. This retrospective review reports the effectiveness of a differential epidural block in the evaluation of these patients. Four patterns of response were identified with the block: 1) reflex sympathetic dystrophy (RSD) (14%), 2) somatic (9%), 3) mixed sympathetic and somatic (27%), and 4) central (50%). The inciting injury in 70% of the patients was a minor strain, sprain, or contusion. Despite accurate diagnosis, the results in compensation cases with pain dysfunction syndrome are exceedingly poor.