A joint actuator assembly comprising: a motor that drives a joint connector for driving a joint of a mobility device; a first stage of speed reduction connected to an output shaft of the motor for providing a speed reduction of the motor output; a second stage of speed reduction linked to an output of the first stage of speed reduction for providing a speed reduction relative to the output of the first stage; and a third stage of speed reduction linked to an output of the second stage of speed reduction for providing a speed reduction relative to the output of the second stage ; wherein the first , second , and third stages operate as a three-stage transmission to provide the output that drives the joint connector; wherein the third stage of speed reduction comprises a cable reel assembly including an output reel and at least one cable element that interconnects the output of the second stage of speed reduction and the output reel ; and wherein the output of the second stage of speed reduction transmits power to the output reel via the cable element to provide the speed reduction of the output of the second stage of speed reduction; characterised in that the cable reel assembly comprises: a first cable reel for winding a first cable , and the first cable further winds around a first output rod of the second stage of speed reduction; and a second cable reel for winding a second cable , and the second cable further winds around a second output rod of the second stage of speed reduction; wherein when the cable reels rotate in a first direction, the first cable reel draws in the first cable and the second cable reel pays out the second cable to provide the third stage of speed reduction. a motor that drives a joint connector for driving a joint of a mobility device; a first stage of speed reduction connected to an output shaft of the motor for providing a speed reduction of the motor output; a second stage of speed reduction linked to an output of the first stage of speed reduction for providing a speed reduction relative to the output of the first stage; and a third stage of speed reduction linked to an output of the second stage of speed reduction for providing a speed reduction relative to the output of the second stage ; wherein the first , second , and third stages operate as a three-stage transmission to provide the output that drives the joint connector; wherein the third stage of speed reduction comprises a cable reel assembly including an output reel and at least one cable element that interconnects the output of the second stage of speed reduction and the output reel ; and wherein the output of the second stage of speed reduction transmits power to the output reel via the cable element to provide the speed reduction of the output of the second stage of speed reduction; characterised in that the cable reel assembly comprises: a first cable reel for winding a first cable , and the first cable further winds around a first output rod of the second stage of speed reduction; and a second cable reel for winding a second cable , and the second cable further winds around a second output rod of the second stage of speed reduction; a first cable reel for winding a first cable , and the first cable further winds around a first output rod of the second stage of speed reduction; and a second cable reel for winding a second cable , and the second cable further winds around a second output rod of the second stage of speed reduction; wherein when the cable reels rotate in a first direction, the first cable reel draws in the first cable and the second cable reel pays out the second cable to provide the third stage of speed reduction. <EOS>