The development of feasible kinematic assessment methods of upper extremity motor function impairment after stroke is clinically extremely important in physiotherapy and rehabilitation engineering. Microsoft Kinect has a potential of a low-cost and compact solution for clinical based assessment of the upper limb motor function after stroke. However, the reliability of Microsoft Kinect in the upper limb motor function assessment has not been well established. Therefore, there is a hesitation in usage of Microsoft Kinect for clinical applications. It is expected that any measurement procedure has the capability to differentiate between pathological and normal performance. On the other hand, the identification of the kinematic metrics that best evaluate impairment of upper-extremity motor function is a key problem of any measurement protocol. Primary objective of our study is, by differentiating pathological performance from the healthy performance and identifying the kinematic metrics that best evaluate the impairment, to demonstrate the robustness/usability of Microsoft Kinect in kinematic analysis of motor performance of stroke patients. We compared the kinematic metrics of the forward reaching movement obtained data recorded from Microsoft Kinect between three stroke patients and two healthy subjects based on the Principal Component Analysis (PCA). In the study, we have defined a new inter-joint coordination index (IJCI) based on PCA to capture inter-joint coordination dynamic of reaching movement in addition to other metrics those have been previously defined and used in literature to quantify upper limb impairment. We observed that the IJCI has significant importance to detect impairment of upper-extremity motor function during a forward reaching task and to discriminate stroke patients from healthy controls. We hope that this paper will promote the acceptance of objective kinematic analysis into routine rehabilitation practices. (C) 2015 Elsevier Ltd. All rights reserved.