Joint booster

The invention belongs to the field of exercise auxiliary instruments, and particularly relates to a joint booster which comprises a first mounting part, a second mounting part and a third mounting part. The second mounting part is used for being attached to the other side of the joint; the rotating device comprises a rotating part which is rotationally connected with the first mounting part; the directional rotating mechanism is arranged between the rotating piece and the second mounting part, and the directional rotating mechanism is assembled to be capable of being matched with the rotating piece so that the second mounting part can directionally rotate relative to the rotating piece; the braking device is movably arranged on the first mounting part, and the braking device is assembled to be capable of being switched between the following two stations: a working condition I, the braking device limits the rotating part so as to enable the second mounting part to directionally rotate relative to the first mou