Relevance of the popliteal angle to hamstring length in cerebral palsy crouch gait

The popliteal angle is a widely used clinical means of assessing hamstring length in cerebral palsy patients. The relevance of the popliteal angle as a measure of hamstring length was assessed in this prospective study. Sixte en patients wi;h cerebral palsy with crouch gait had their conventional and modified popliteal angles measured by nine observers on two separate occas ions. With use of the conventional and modified forms of the test, 74 and 7 0%, respectively, of the observed variability was inter- and intraobserver related. The range of SDs for each observer using the conventional test was 7.1-13.6 degrees (average 10.9 degrees), and with use of the modified form of the test, the range was 6.3-4.2 degrees (average 10.5 degrees). The max imum hamstring length of each subject during gait was determined by three-d imensional modelling of their lower limbs. The modified popliteal angle mea surements of the most repeatable observer demonstrated an inverse relations hip between modified popliteal angle and maximum hamstring length (p < 0.01 ) and muscle excursion (p < 0.01). Only 10 of 32 limbs had short medial ham strings.