A driven joint unit for a robot has two drive rollers mounted in a frame, driven by a motor in each instance. There is also a differential cone wheel stage, in each instance which consists of two deflection cone wheels, forming a first pair of cone wheels, mounted coaxially in the frame, preferably parallel to the axes of the coaxial drive rollers, whose axes, which extend in the direction of a first robot axis, form a first joint axis. There are also two coaxially disposed power take-off wheels, forming a second pair of cone wheels, the axes of which extend in a second joint axis perpendicular to the first joint axis. One of the two power take-off wheels is rigidly connected with the power take-off, and the other opposite coaxial power take-off cone wheel is mounted to be rotationally freely movable. There is also a number of biased tension means of which at least respectively two tension means are attached to the two drive rollers and are directed in opposite directions. These tension means are guided around a part of the adjacent deflection cone wheels in each instance. Said at least respectively two tension means are attached to said rotationally freely movable power take-off cone wheel and to said power take-off wheel that is rigidly connected with the power take-off, respectively.