Nineteen patients with anterior knee pain without the classical features of reflex sympathetic dystrophy (RSD) were investigated by local anesthetic sympathetic blockade. Scintigraphy was performed before the sympathetic blockade in all the cases, and the scintigraphic appearances were correlated with the clinical response. Eleven patients responded to the blockade (9 good and 2 fair). Only 1 out of 10 patients with increased scintigraphic uptake failed to respond, whereas 7 out of 9 patients with normal uptake failed to respond. Our study suggests that a sympathetically mediated component may exist in patients with anterior knee pain without RSD, and that scintigraphy is useful in identifying those patients for whom sympathetic blockade may be helpful.