Actuator for physical therapy

A robotic system comprising:

• a first linkage and a second linkage;
• a joint coupling the first linkage to the second linkage;
• and
• at least one cable;
• wherein the joint includes a motor having a shaft, a strain wave gear having a circular spline, a first conduit, and a bearing;
• wherein the motor is configured to rotate the shaft in a first direction;
• wherein the at least one cable passes through the bearing and into the second linkage but does not pass through either of the strain wave gear or the motor;
• wherein the first conduit is configured to rotate about a longitudinal axis;
• wherein (a) the strain wave gear is distal to the motor and proximal to the first conduit, (b) the first conduit is proximal to the bearing, and (c) the second linkage is distal to the first linkage;
• wherein the first conduit comprises:
• (a) a first outer wall;
• (b) a second outer wall;
• (c) an inner wall which couples the first and second outer walls to each other;
• and
• wherein the first and second outer walls and the inner wall collectively define a channel that extends about the longitudinal axis;
• wherein a plane, which is orthogonal to the longitudinal axis, intersects the inner wall and the channel.