Fig. 4

The mean difference of the measured joint angles between the developed system and universal goniometer. Each plot represents the angle measured by the universal goniometer minus the angle calculated by the developed system. The top left panel represents the mean differences in the measured angles between the two methods using the Bland–Altman plots, with all joint movement data integrated. The other five panels represent the mean differences for each joint: shoulder (top center), elbow (top right), hip (bottom left), knee (bottom center), and trunk (bottom right). X and Y axes show the mean value of the two measurement methods and the mean difference between them, respectively. The middle solid line represents the mean differences; the top and bottom solid lines show the Limits of Agreement. The dotted lines show the 95% confidence intervals of the mean differences and the Limits of Agreement.