Intertester reliability and concurrent validity of fluid-based and universal goniometers for active knee flexion.

This study was designed 1) to determine the intertester reliability of the universal goniometer and the fluid-based goniometer and 2) to establish the concurrent validity of the fluid-based goniometer. Two testers measured active knee flexion of 20 healthy subjects (15 women, 5 men) using both instruments. The subjects had a mean age of 24.8 years (s = 5.5) and reported no previous history of pathological conditions of the right lower extremity. Using a correlational design, high intertester reliability was established for each instrument (universal goniometer, r = .87; fluid-based goniometer, r = .83). The concurrent validity of the fluid-based goniometer was also good for both testers (tester A, r = .83; tester B, r = .82). When the data were subjected to t tests, significant differences were found between the instruments for each tester (p less than .05). The results suggest that similar measurements will be obtained between therapists using the universal and fluid-based goniometers; however, the two instruments cannot be used interchangeably in the clinic.