A prosthetic hand system may include a plurality of prosthetic fingers and a prosthetic thumb. The prosthetic hand system may include a thumb drive mechanism that may be used to actuate the prosthetic thumb. In some examples, the thumb drive mechanism may be configured to enable the prosthetic thumb to perform a pinching or grasping motion and a release motion. The prosthetic hand system may also include a backlock that enables the prosthetic thumb to maintain pinching or gripping pressure after a motor has been disengaged. The prosthetic hand system may also include a gear lock that may be configured to lock a finger joint. The prosthetic hand system may also include an adaptive gripping joint that may be located on each prosthetic finger. In some examples, the adaptive gripping joint may be configured to passively adapt the plurality of prosthetic fingers to one or more differently shaped objects.