A vacuum assisted suspension system includes a prosthetic foot and a pump mechanism connected to the foot and fluidly couplable to a prosthetic socket. The pump mechanism includes an elongate pivoting member rotatable relative to the prosthetic foot about a joint and including a distal recess. A piston is connected to the foot and is movably received in the recess. A fluid chamber is defined between the piston and the interior of the recess. When no weight is placed on the foot a volume of the fluid chamber is zero or near-zero and when weight of a user is placed on the prosthetic foot the pivoting member rotates away from the piston and expands the volume of the fluid chamber to draw fluid into the fluid chamber from the prosthetic socket.
