Abstract: A prosthesis for the CMC joint of a thumb therefore includes a metacarpal component that has a first articular surface and a stem configured for insertion and anchoring into a metacarpal canal of a thumb metacarpal bone. The stem has a dorsal surface and an opposing volar surface. Each of the dorsal surface and the volar surface is defined by a proximal region and a distal region. The proximal region of the volar surface has a volar taper angle that is greater than distal region of the volar surface and a dorsal taper angle of proximal region of the dorsal surface is less than the volar taper angle of the proximal region of the volar surface. The prosthesis further includes a trapezial component having a second articular surface cooperating with the first articular surface. The trapezial component is configured to be coupled (e.g., anchored) to a trapezium bone.