An example robot includes: a leg having an upper leg member and a lower leg member coupled to the upper leg member at a knee joint; a screw actuator disposed within the upper leg member, where the screw actuator has a screw shaft and a nut mounted coaxial to the screw shaft such that the screw shaft is rotatable within the nut; a motor mounted at an upper portion of the upper leg member and coupled to the screw shaft; a carrier coupled and mounted coaxial to the nut such that the nut is disposed at a proximal end of the carrier; and a linkage coupled to the carrier, where the linkage is coupled to the lower leg member at the knee joint.