An air expulsion pump for a prosthetic socket adapted to be worn on a residual limb of an amputee. The pump includes an elastomeric housing which fits snugly in a well defined in the lower end of the socket. The pump is easy to install by simply sliding it into the well. The pump has an upper surface commensurate with the inside surface of the socket in that both surface have the same radius of curvature. The pump includes an elastomeric spring member and two check valves that together with the elastomeric housing exert a continuous vacuum within the prosthetic socket. When donned by the user, the pump provides continuous total contact between the socket and the residual limb of the user as the user ambulates.
