Our Modified Box and Blocks Test with Motion Capture allows us to analyze the kinematics of arm and trunk motion during this task. When a prosthetic user moves blocks from one side of the box to the other, there are significant compensations of body movement that occur. The goal of developing advanced prosthetic devices with better control and motion capability is to reduce the abnormal movements seen in prosthetic users and provide more natural arm and trunk movement. New sensitive assessment metrics will help clinicians and prosthetic users decide which prosthetic devices are best to improve function and to minimize long term problems.