Reflex sympathetic dystrophy of the knee after sensory nerve injury.

Reflex sympathetic dystrophy (RSD) of the knee is an extremely difficult problem to treat. This study examined the possible relationship between isolated injury to the infrapatellar branch of the saphenous nerve (IPBSN) and the etiology and natural course of RSD. Thirty-five patients with clinically significant sympathetic dystrophy of the knee were examined retrospectively. All patients (100%) had clinical evidence of insult to the IPBSN. Thirty-three patients (94%) were found to have vasomotor instability as measured by isolated cold stress testing (ICST). All patients in this population of 33 were treated with vasoactive therapies. Subjective improvement was noted in 20 patients (p = NS). Initial ICSTs of improved and unimproved patients were compared. Baseline temperatures were significantly warmer in patients who improved with therapy (p less than 0.05), and a warmer trend was evident throughout all phases of the test in those who improved compared with those who did not. Eighty percent of patients treated within 1 year improved with one or more vasoactive therapies, whereas only 44 percent improved when treatment was started after 1 year, indicating a significant population difference (p less than 0.05).