an instrument for setting ligament tension between a distal femur and a proximal tibia has a rod mounted on a femur . the rod has an extension extending along a first axis . a first drive element is mounted on the distal femur and is rotatable about a second axis . a body is rotatably mounted on the rod extension for rotation about the first axis . the body has a second drive element engaging the first drive element and a third drive element extending about a third axis offset from the first and second axes . a ligament tensioning element is mounted on the body and has a foot for engaging a posterior condyle of a femur and has a fourth drive element . a fifth drive element engages both the third and fourth drive elements for moving the ligament balancer with respect to the body along the third axis .