A dynamic spacer is provided for measuring flexion-extension gap during total knee arthroplasty. The dynamic spacer includes a first planar member having a lower tissue engaging surface, and a second planar member having an upper tissue engaging surface. A tensioner is disposed between the first planar member and the second planar member for applying a tensile force acting upon the first and second planar members. The tensioner is attached to the first and second planar members, such that the first planar member is held substantially parallel to the second planar member in the absence of compressive load. The dynamic spacer allows for accurately measuring flexion-extension gaps and angular deviation in flexion indicating the appropriateness of femoral rotation.