A lockable joint such as a lockable ball-and-socket joint comprising a first arm (14) having a swivel head (30) and a socket (32), the swivel head (30) being pivotably mounted to the socket (32), and a locking device (90) arranged for locking the swivel head (30) with respect to the socket (32), the locking device (90) having a piston (70&prime；), a pressure gas source (64), and an actuating device (92) arranged for reversibly disconnecting the piston (70&prime；) from the pressure gas source (64) where in the pressure gas source is a gas cartridge (64).
