A surgical instrument support system has a support frame supported by three arms. Each arm has a plurality of ball and socket members strung in series along a cable. The arms are also connected to bases mountable to the patients limb on the proximal and distal sides of the joint. Actuators are provided for each arm to change the tension in the cables to change the stiffness of each arm. The support system can be part of a surgical instrument system that includes a plurality of resection guides mountable to the support frame.
