The accuracy of the Microsoft Kinect in joint angle measurement

The Microsoft Kinect is a cheap consumer device capable of markerless body segment tracking. While it was not originally designed for research applications, studies have been performed which utilise its capabilities. In order to better define the suitability of the device in a clinical and biomechanical context, a study was performed which assessed the accuracy of the device in 12 separate movements and for two different software-based tracking algorithms (IPIsoft and NITE). The movements were chosen to represent a variety of joint motions and speeds. Ten participants (height, 185 ± 6 cm; mass, 77 ± 9 kg) performed each movement while the Kinect and a Motion Analysis Corporation capture system recorded simultaneously. The procedure was performed twice, once for each tracking algorithm. Median values for RMSE, maximum error, systematic bias and proportional bias were 12.6°, 58.2°, 4.38° and 1.15°, respectively, for the IPIsoft algorithm and 13.8°, 63.1°, 3.16° and 1.19°, respectively, for the NITE algorithm. While maximum errors are high the system has many advantages over existing multi-camera markerless tracking systems. The Kinect could be used in low speed analysis of simple human motions where cost and ecological validity are of high priority.