Flexible electrogoniometers: kinesiological advantages with respect to potentiometric goniometers

Unlike conventional potentiometric goniometers, flexible electrogoniometers do not suffer from any alignment problems with respect to the joint axis. We hypothesized that flexible goniometers provide more valid measurements in that they avoid some biomechanical pitfalls. With both devices simultaneously we measured the movements of dorsal flexion of the ankle and flexion of the knee in three healthy subjects. In the various subjects, this comparison showed that the flexible goniometers signalled ankle excursion greater by 19-40% with the foot remaining in neutral position or being simultaneously pronated, and lower by 10-21% with the foot being simultaneously supinated. At the knee the flexible goniometers signalled a flexion greater by 24-32%, with respect to potentiometric goniometers. Biomechanical considerations support the validity of records taken with flexible goniometers, potentiometric measures being biased by (a) multijoint, multiplane motions underlying foot dorsal flexion, and (b) multiaxis motion underlying knee flexion.