The miniaturization of ultrasound technology provides an opportunity to utilize imaging in new point-of-care settings. The goal of this study was to investigate the feasibility of a universal serial bus (USB) based ultrasound transducer for dynamic imaging of the muscle function during gait. Axial strain of the rectus femoris muscle was measured during gait using the portable USB probe and compared against a conventional ultrasound system with a high-resolution linear array transducer. A high speed camera was also used to track the gait pattern for each subject and measure the relative motion of the transducer during gait. Our results indicate a good correlation (R2 = 0.63) between the conventional ultrasound system with linear transducer and the portable USB transducer based ultrasound system over all trials, with <4% difference between the two systems. The USB based ultrasound system demonstrated good good repeatability during two separate sessions (ICC2,1 = 0.67, p<0.05). Our preliminary results indicate that this novel method can complement conventional clinical measures of functional biomechanics and can be used in a point-of-care setting for rehabilitation applications. © 2013 IEEE.