A protective device for a joint, particularly for a knee, comprising a first frame to which a second frame is articulated by means of a pair of hinges that during use are arranged proximate to the two sides of the joint, the hinges being constituted by a first base and a second base, which are associated respectively with the first and second frames and are rotatably connected to each other by means of a first arm and a second arm, which are mutually crossed. The ends of the first arm are rotatably associated with the first and second bases, both by means of substantially hemispherical mutual engagement surfaces one end of the second arm is associated rotatably with the first base by means of a substantially hemispherical mutual engagement surface and the other end of the second arm is associated with the second base by means of a substantially flat mutual engagement surface.
