Fig. 15 in Anatomical Study of the Right Forearm and Hand of One Western Gorilla (Gorilla gorilla) for Comparison with Humans with Respect to Motions of the Thumb and Fingers

Fig. 15. The mechanism to block hyperextension of the MP joint with the function of the sagittal band. A. When the finger is flexed, the sagittal band passes over the joint axis of the metacarpal head in coordination with the distalward movement of the extensor tendon; B. When the MP joint is extended and surpasses the range of extension, the traction force of the finger extensor is blocked with the tightened sagittal band that transmits the force palmarward so that the proximal phalanx base does not move further to hyperextension.