Bharadwaj Ravi, Manak Kapoor, Darren Player
MBBS, MSc (Musculoskeletal Science), University College London, Gower Street, London, United Kingdom. E-mail: dr.bravi@yahoo.com
DOI: 10.2340/16501977-2780

Objective: Measurement of joint angles is usually performed using a simple goniometer, which can often be time-consuming and inaccurate, however smartphones can measure angles, this technology could be used to measure joint position. Studies of smartphone applications for this purpose lack consistency and homogeneity. The aim of the current study is to analyse the reliability and accuracy of 3 inertial motion unit-based smartphone applications for goniometric measurement, using 3 different industry standards as external controls.
Methods: In the first 2 phases of the study, measurements of angles between 90° and 165° (simulating knee extension) using 3 smartphone applications were analysed against the 3 industry standards. In the third phase, the smartphone’s raw data was individually analysed against a digital inclinometer across the x, y and z axes.
Results and conclusion: Results from the 3 phases of this study indicate a high degree of reliability and validity of the applications compared with the industry standards, with no clinically significant deviations. Thus, this technology could be used in a clinical setting. However, further clinical research, focussing on joint motions with greater than a single degree of freedom, is required before the use of such applications for joint position measurement in clinical practice.

The range of movement of various joints in the human body is regularly measured in a clinical setting, using a traditional angle measurement device (a goniometer), during functional assessments by doctors and physical and occupational therapists. However, such measurements can often be time-consuming and inaccurate. This study analysed the accuracy of smartphone apps for measuring joint angles compared with a goniometer. The results show that smartphone apps could be a good alternative for measuring joint angles.