An embodiment includes simultaneously supplying direct current energy to recondition cartilage of a knee joint while simultaneously protecting that cartilage by supplying alternating current energy to stimulate muscle tissue contralateral to the cartilage to at least partially decompress the cartilage and at least partially support the joint. The adapter may be operable to couple with the head of a bone screw and may comprise a plurality of threads to permit coupling with holes located in a locking plate. It is judged that the jam is caused on the basis of the loss of synchronism of the motor if the jam is detected by the jam detecting means when the loss of synchronism is judged by the loss of synchronism detecting means.