Objective: To compare the reliability of measurements of hip motions obtained with two instruments, an electronic inclinometer and a two-arm goniometer, and to investigate whether the two instruments, and different body positions, produce the same measurement data.
Methods: Maximal active and passive hip movements were measured simultaneously with both instruments, in nine subjects during 10 consecutive measurements at short intervals.
Results: Intra-observer variability was lower with the inclinometer in measurements of passive hip rotations. The two instruments showed equal intra-observer variability for hip movements in general. The inclinometer showed lower inter-observer variability in the measurements of active internal rotation. More rotational movement was measured with the two-arm goniometer; more extension and flexion with the inclinometer. Also, more rotational movement was found in the prone position compared to sitting and supine positions.
Conclusions: The inclinometer is more reliable in measurements of hip rotation. For hip movements in general the two-arm goniometer is just as accurate when used by only one observer. The two instruments, and some positions, are not interchangeable during consecutive measurements.