origin: distal 1/4 of the volar (ant) surface of the ulna;
insertion: distal 1/4 of the volar surface of the radius;
action: pronates the forearm;
nerve supply:   Median ,   C7 ,   C8 ,   T1 ;
synergists:   Pronator Teres 

Stabilization of the distal ulna by transfer of the pronator quadratus origin.