A surgical instrument comprising: a shell assembly including: a shell housing ; a plurality of staples ; a staple pusher configured to eject the plurality of staples from the shell housing; a staple actuator configured to engage the staple pusher; a knife member ; and a knife carrier supporting the knife member; and an adapter assembly including: a cam ring movable between an engaged position in which the knife carrier engages the cam ring and a disengaged position in which the knife carrier is disengaged from the cam ring; characterised in that the adapter assembly further comprises: a staple band configured to couple to an actuation mechanism for axial displacement, the staple band configured to releasably engage the staple actuator; and a knife band at least partially received within the staple band , the knife band configured to couple with an actuation mechanism for axial displacement; and in that the cam ring is rotatably supported about the knife band , the cam ring being rotatable between the engaged position in which the knife carrier engages the cam ring for concomitant axial displacement with the knife band and the disengaged position. a shell assembly including: a shell housing ; a plurality of staples ; a staple pusher configured to eject the plurality of staples from the shell housing; a staple actuator configured to engage the staple pusher; a knife member ; and a knife carrier supporting the knife member; and a shell housing ; a plurality of staples ; a staple pusher configured to eject the plurality of staples from the shell housing; a staple actuator configured to engage the staple pusher; a knife member ; and a knife carrier supporting the knife member; and an adapter assembly including: a cam ring movable between an engaged position in which the knife carrier engages the cam ring and a disengaged position in which the knife carrier is disengaged from the cam ring; characterised in that the adapter assembly further comprises: a staple band configured to couple to an actuation mechanism for axial displacement, the staple band configured to releasably engage the staple actuator; and a knife band at least partially received within the staple band , the knife band configured to couple with an actuation mechanism for axial displacement; and in that the cam ring is rotatably supported about the knife band , the cam ring being rotatable between the engaged position in which the knife carrier engages the cam ring for concomitant axial displacement with the knife band and the disengaged position. a cam ring movable between an engaged position in which the knife carrier engages the cam ring and a disengaged position in which the knife carrier is disengaged from the cam ring; characterised in that the adapter assembly further comprises: a staple band configured to couple to an actuation mechanism for axial displacement, the staple band configured to releasably engage the staple actuator; and a knife band at least partially received within the staple band , the knife band configured to couple with an actuation mechanism for axial displacement; and in that the cam ring is rotatably supported about the knife band , the cam ring being rotatable between the engaged position in which the knife carrier engages the cam ring for concomitant axial displacement with the knife band and the disengaged position. a staple band configured to couple to an actuation mechanism for axial displacement, the staple band configured to releasably engage the staple actuator; and a knife band at least partially received within the staple band , the knife band configured to couple with an actuation mechanism for axial displacement; and in that the cam ring is rotatably supported about the knife band , the cam ring being rotatable between the engaged position in which the knife carrier engages the cam ring for concomitant axial displacement with the knife band and the disengaged position. <EOS>