THE INVENTION RELATES TO A LOCKABLE JOINT, ESPECIALLY A LOCKABLE BALL-AND-SOCKET JOINT, COMPRISING A FIRST ARM (14) HAVING A SWIVEL HEAD (30), 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'), A PRESSURE GAS SOURCE (64), AND AN ACTUATING DEVICE (92) ARRANGED FOR REVERSIBLY DISCONNECTING THE PISTON (70') FROM THE PRESSURE GAS SOURCE (64) WHERE IN THE PRESSURE GAS SOURCE IS A GAS CARTRIDGE (64).