To investigate the interexaminer reliability of the prone extended relative leg-length check as described by Activator Methods, Inc.


Thirty-four subjects were selected from a pool of 52 consecutive patients visiting a private chiropractic office.


Exclusion criteria included congenital or acquired conditions known to affect lower extremity length and inability to lie prone for a 10-minute period. Two experienced chiropractors who specialize in Activator Methods and are “advanced-proficiency rated” by Activator Methods, Inc. assessed each patient in random order for leg length inequality. Findings were recorded as left short leg, equal leg length, or right short leg.


The data for 34 subjects were organized in a 3 x 3 contingency table. Total agreement was 85%. A simple, unweighted kappa value yielded kappa = 0.66. A disproportionately greater number of right short leg findings than left short leg findings were observed by both examiners. In only 2 instances were equal leg lengths observed, and both were detected by the same examiner. Because examiners found only 2 of 34 subjects with equal leg lengths, several secondary analyses involving data reductions were conducted. The resulting kappa values were similar to the 3 x 3 analysis.


There was good reproducibility between 2 examiners by using the Activator Method to detect leg length inequality in the prone extended position. This study does not address the validity or clinical significance of the measurement method. Future studies should include larger numbers, a wider variety of subjects, and a diversity of examiners.

J Manipulative Physiol Ther. 1999 Nov-Dec;22(9):565-9. [PMID:10626698]

Author information: Nguyen HT, Resnick DN, Caldwell SG, Elston EW Jr, Bishop BB, Steinhouser JB, Gimmillaro TJ, Keating JC Jr. Los Angeles College of Chiropractic, Whittier, Calif, USA.