The cartridge assembly (100) includes a housing (110), a pusher member (160), a fastener cartridge body (120), a circular cartridge buttress member (130), and a retaining ring member (140). The pusher member is supported within the housing and movable between a first position and a second position. The fastener cartridge body is supported on the housing and has a tissue engaging surface (122) that extends to an annular edge (122a). One or both of the housing and the fastener cartridge body define an annular containment groove (118). The circular cartridge buttress member has a body portion (132) and an extension portion (134). The body portion is supported on the tissue engaging surface of the fastener cartridge body. The extension portion extends from the body portion and over the annular edge of the tissue engaging surface. The retaining ring member is secured within the containment groove to releasably secure the extension portion of the circular cartridge buttress member to the cartridge assembly.
