Validity and inter-operator reliability using EasyAngle for mobility measurement of people with hip osteoarthritis

Authors: Karin Fröjd, University of Uppsala

Year of study: 2016

Number of subjects: Thirty-five subjects (20 women)


The aim of this study was to examine the digital tool Easy Angle regarding its concurrent validity and interrater reliability measuring active and passive range of motion in people with hip osteoarthritis.


Thirty-five subjects (20 women) were included in the study. Concurrent validity was compared with a goniometer. Inter-rater reliability was tested between two
experienced physiotherapists and included both active and passive hip joint movement in the directions of flexion, abduction, internal rotation, and external rotation in people with hip osteoarthritis. To evaluate the results Intraclass Correlation Coefficient (ICC) and Bland Altman Agreement Test was used.


The validity of the Easy Angle proved to be excellent (ICC2.1 0.85-1.0) regardless of the direction of movement in terms of both active and passive mobility. Also
inter-rater reliability (ICC3.1 0.83 to 0.96) were observed to be excellent at most testing moments apart from the active abduction and active external rotation, where the results were fair to good (ICC3.1 0.67 to 0.69). Generally abduction and external rotation showed the greatest uncertainty in the measurements according to Limits of Agreement (LoA).


The results indicate that experienced physiotherapists with high reliability and validity can use the digital tool Easy Angle for range of motion measurements in
people with hip osteoarthritis. Directions abduction and external rotation seems to be the movements that have the highest uncertainty in the measurements.

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