# On the Use of a Depth Camera for the Assessment of Upper Extremity Movements in Healthy Individuals

## TL;DR

This study evaluates the reliability of a Microsoft Kinect camera for measuring upper body movement in healthy people, finding it works well for some movements but has limitations in others.

## Contribution

The study provides new reliability data for the Kinect V2 camera in assessing upper extremity range of motion in healthy individuals.

## Key findings

- Kinect V2 showed moderate to excellent within-day reliability for upper extremity movements.
- Between-day reliability was lower, with high minimal detectable change values for some movements.
- Shoulder adduction tracking failed in 36.7% of participants due to self-occlusion issues.

## Abstract

Upper extremity impairments often lead to reduced joint range of motion (ROM), making reliable assessment essential for rehabilitation planning. This study investigated the within-day and between-day reliability of the Microsoft Kinect V2 depth camera for active upper extremity ROM assessment in 30 healthy adults. Ten predefined shoulder and elbow movements were recorded, and joint angles were computed using a custom vector-based algorithm. Within-day reliability ranged from moderate to excellent (ICC: 0.754–0.953), while between-day reliability ranged from moderate to good (ICC: 0.654–0.881). Absolute reliability varies substantially across movements. The SEM% values ranged from 2.1% to 17.3% within-day and from 2.8% to 23.6% between-day. The between-day MDC values were particularly high for certain movements (e.g., >20° for shoulder extension and >50° for elbow flexion), indicating limited sensitivity to detect small clinical changes. Additionally, shoulder adduction could not be reliably analyzed in 36.7% of participants due to self-occlusion-related tracking instability, highlighting a practical limitation of the Kinect V2 for certain upper extremity movements. These findings suggest that Kinect V2-based ROM assessment demonstrates acceptable reliability for large-amplitude planar movements under controlled conditions but shows substantial limitations for rotational and occlusion-prone tasks. The device may be suitable for research or screening applications; however, caution is warranted when interpreting small changes in clinical settings.