A joint actuator assembly includes a motor, a rotating driving member driven by the motor for driving a driven component, and a transmission assembly located between the motor and the rotating driving member that provides speed reduction from the motor to the rotating driving member. The rotating driving member comprises a magnetic coupling including a plurality of magnetic elements that are configured to magnetically couple with an opposing magnetic coupling of the driven component. The actuator and driven component may be combined into a mobility device including a magnetic coupling system having a first magnetic coupling on the actuator that magnetically couples to a second magnetic coupling on the driven component. The magnetic coupling system includes plurality of magnetic elements located as part of one or both of the first and second magnetic couplings. The first and second couplings have opposing mating surfaces that join together in a coupled position.