Lasègue's sign

[lə-sĕgz, lä-]
n.
  1. An indication of lumbar root or sciatic nerve irritation in which dorsiflexion of the ankle of an individual lying supine with the hip flexed causes pain or muscle spasm in the posterior thigh.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.