The invention relates to an orthopaedic aid, in particular to a prosthesis (58) or orthosis comprising an orthopaedic fluid damper (10) with a displacement chamber (14) formed in a housing (12), with a piston (16) mounted in the displacement chamber (14), with a fluid reservoir for a fluid (20), with a return flow conduit (22) connecting the displacement chamber (14) to the fluid reservoir, with a valve (24) that can adopt an open position and a closed position, in which it at least partially closes the return flow conduit (22), and with a joint (72) that has a first branch (60) and a second branch (66), wherein the first branch (60) is connected to the housing (12) and the second branch (66) is connected to the piston (16). A device (84) is also provided for detecting a joint force (FB) acting on the joint, which device (84) is designed to bring the valve (24) to the closed position when the joint force (FB) exceeds a predefined threshold value. The invention also relates to a method for control of the aid and a fluid damper (10) fitted therein.
