Unilateral leg edema is almost always caused by a disease process that obstructs the venous or lymphatic drainage in the leg or pelvis but can also occur in chronic regional pain syndrome (CRPS).1 We report unilateral leg edema that was a consequence of CRPS induced by an S1 radiculopathy (type 2 CRPS). We show that the etiology of the edema was neurogenic because a posterior tibial nerve block abolished the edema distal to the block.