A vacuum suspension system includes a pump mechanism operatively connectable to a prosthetic socket. The pump mechanism has a first member and a second member. First and second fluid chambers are located between the first and second members. The second fluid chamber is fluidly separate from the first fluid chamber, and arranged for fluid communication with the socket. An increase in volume of the first fluid chamber mechanically expands the second fluid chamber, which, in turn, creates a vacuum pressure in the second fluid chamber.
