Concurrent validity of evaluating knee kinematics using Kinect system during rehabilitation exercise

Squats, ascending and descending stairs, and lunges are three functional movements popularly used in clinical rehabilitation. This study aimed to analyze the validity of the Kinect v2 for assessing the kinematics of three functional knee movements. An intelligent program was developed for real-time kinematic evaluation of the knee joint using the Kinect v2 system. Based on image recognition technology, images from the Kinect v2 depth camera were used to develop a kinematic evaluation program for knee joint movements. The kinematics of 30 healthy volunteers during stair ascent and descent, squatting, and lunging movements were collected synchronously with both VICON and Kinect systems. The peak knee angles in the sagittal and coronal planes were extracted and analyzed. A paired samples t-test and the relative coefficient within the groups were used for statistical analysis of the validity of the Kinect compared to the VICON. There was no significant difference (p ​> ​0.05) in bilateral knee flexion angle when lunging. No significant difference (p ​> ​0.05) was found in left knee flexion during squatting exercises. Although the Kinect generally underestimated knee flexion and valgus, it displayed excellent consistency and good to excellent agreement with the VICON motion analysis system. The results demonstrated that the Kinect based measurement tool for analyzing knee kinematics has the potential to be an effective clinical training device for maintaining knee alignment during exercise.