A tension mechanism for a robotically-controlled medical device measures the tension applied to an actuation tendon to provide feedback to a robotic controller. In one embodiment, the device comprises an elongated instrument, an elongated member, and a base. The elongated member is coupled to the distal end of the elongated instrument, configured to actuate the distal end of the elongated instrument in response to tension in the elongated member. The base is located at the proximal end of the elongated instrument, and comprises a first redirect surface that redirects the elongated member. The first redirect surface is coupled to a lever element that is configured to exert a reactive force on a sensor in response to tension in the elongated member.
