Shoulder impingement syndrome, the compression of the supraspinatus tendon between the acromion and the humeral head, is a common injury afflicting both ablebodied and paraplegic populations. Currently, techniques for accurately quantifying joint space changes are extremely limited. This study proposes a new methodology for quantifying the shoulder joint space change during a functional loading task, using threedimensional magnetic resonance imaging (MRI). Loaded and unloaded joint surfaces were digitized and modeled with a numerical technique known as thin-plate spline. The most reliable and precise measure of shoulder joint space was determined to be change in median proximity. A modified version of this methodology using three different upper extremity postures was applied to a group of healthy and injured subjects to determine if there were significant differences between the two groups. Upper extremity abduction caused significant differences in the acromiohumeral joint space change when comparing healthy and injured subjects.