A socket assembly for a prosthetic limb is provided. The socket assembly includes an elongated upper circumferential section having an open upper end and a distal end, the distal end having a distal diameter. The assembly further includes an intermediate section extending outwardly from the upper section to a maximum diameter that is larger than the distal diameter of the first upper section, the intermediate section tapering inwardly from its maximum diameter to a lower rim region. A distal section extends from the lower rim region to a base of the socket, and a one-way valve is in fluid communication with an interior of the socket assembly. A flexible diaphragm is configured to engage walls of the intermediate section.