A robot arm has a transmission output-side mating running surface on which a dynamic contact seal that seals off the transmission casing in a lubricant-tight manner is seated. A gap is determined by a main bearing arrangement between an upstream link and a downstream link, to which an output flange of a joint torque sensor is coupled, is sealed off by means of a further dynamic seal, with the objective of increasing the accuracy of the torque measurement by optimizing the secondary force flows.