A circular stapler comprising: a handle assembly; an elongate body extending from the handle assembly; and, a cartridge assembly mounted on a distal end of the elongate body, the cartridge assembly including a pusher assembly and a knife assembly, the knife assembly configured to be initially detached from the pusher assembly in a first stroke, and subsequently attached to the pusher assembly in a second stroke, wherein: the knife assembly includes a knife carrier, a knife supported on and extending distally from the knife carrier and a snap ring supported around a proximal portion of the knife carrier, the knife carrier includes an annular groove configured to accommodate the snap ring when the snap ring is in a radially compressed condition so that the knife assembly is movable relative to the pusher assembly; wherein the annular groove is configured to accommodate the snap ring when the snap ring is in an uncompressed condition, the knife carrier further includes a step formed in the annular groove configured to engage the snap ring when the snap ring is in the uncompressed condition, and the pusher adapter includes a ridge formed about an inner surface thereof configured to engage the snap ring of the knife assembly when the snap ring is in the uncompressed condition so that the knife assembly is fixed relative to the pusher assembly, wherein the step is configured to prevent radial compression of the snap ring during the second stroke, which is a tissue cutting stroke. a handle assembly; an elongate body extending from the handle assembly; and, a cartridge assembly mounted on a distal end of the elongate body, the cartridge assembly including a pusher assembly and a knife assembly, the knife assembly configured to be initially detached from the pusher assembly in a first stroke, and subsequently attached to the pusher assembly in a second stroke, wherein: the knife assembly includes a knife carrier, a knife supported on and extending distally from the knife carrier and a snap ring supported around a proximal portion of the knife carrier, the knife carrier includes an annular groove configured to accommodate the snap ring when the snap ring is in a radially compressed condition so that the knife assembly is movable relative to the pusher assembly; wherein the annular groove is configured to accommodate the snap ring when the snap ring is in an uncompressed condition, the knife carrier further includes a step formed in the annular groove configured to engage the snap ring when the snap ring is in the uncompressed condition, and the pusher adapter includes a ridge formed about an inner surface thereof configured to engage the snap ring of the knife assembly when the snap ring is in the uncompressed condition so that the knife assembly is fixed relative to the pusher assembly, wherein the step is configured to prevent radial compression of the snap ring during the second stroke, which is a tissue cutting stroke. the knife assembly includes a knife carrier, a knife supported on and extending distally from the knife carrier and a snap ring supported around a proximal portion of the knife carrier, the knife carrier includes an annular groove configured to accommodate the snap ring when the snap ring is in a radially compressed condition so that the knife assembly is movable relative to the pusher assembly; wherein the annular groove is configured to accommodate the snap ring when the snap ring is in an uncompressed condition, the knife carrier further includes a step formed in the annular groove configured to engage the snap ring when the snap ring is in the uncompressed condition, and the pusher adapter includes a ridge formed about an inner surface thereof configured to engage the snap ring of the knife assembly when the snap ring is in the uncompressed condition so that the knife assembly is fixed relative to the pusher assembly, wherein the step is configured to prevent radial compression of the snap ring during the second stroke, which is a tissue cutting stroke.