The controllability of the unloaded human finger with superficial or deep flexor.

The unloaded human finger with a taut deep flexor functions as a bi-articular chain, because the angulations of the distal two joints are mechanically coupled. In this chain two flexors exist: the superficial and deep flexor. However, for elementary control of the unloaded finger, only one flexor is required. This puts forward the question of which flexor is most suited for unloaded finger control. In the present paper it is argued that due to the chiasma tendinum and the coupled rotations of the distal two joints, the deep flexor is anatomically better positioned than the superficial flexor for optimal unloaded finger control.