A single-camera motion analysis system, referred to as Behrend motion analysis system, is developed to study 3D knee kinematics in vertical jump. The system was tested and compared with 3D commercial motion system Xsens Awinda. The waveform of flexion/extension measured by Behrend motion analysis system exhibits a high degree of similarity to the waveform measured by Xsens Awinda system (R2>0.97).