An adapter module (2) configured to be attached, by a predetermined number of screws (4), to a socket member (6) of a prosthetic sleeve (8), into which sleeve (8) an amputation stump of a prosthesis user is to be inserted. The adapter module (2) comprises a module body (10) provided with a washer space (12) structured to provide room for a disc-shaped connection washer (14), the washer space (12) has an extension to provide for movement of the connection washer (14) within a plane essentially perpendicular to a longitudinal axis A of said prosthetic sleeve (8) prior the connection washer (14) is fixated in a determined position. The connection washer (14) is provided with a through-going first opening (16) structured to receive a washer attachment screw (18) such that the screw essentially extends along said longitudinal axis A. The through-going first opening (16) is preferably positioned off-centered of the washer (14) in order to maximize movement of the washer in all directions within the plane.