A robot-aided knee arthroplasty system comprising: an end effector of a robotic arm to couple to a femur of a knee joint with a soft tissue balancing component that permits the femur to freely rotate while coupled to the end effector; a robotic controller to: cause the robotic arm to apply a pulling force to the femur using the end effector to increase a gap distance between a first point on the femur and first point on a tibia of the knee joint; measure the gap distance between the first point on the femur and the first point on the tibia and a rotation of the femur as the robotic arm applies the pulling force to the femur using the end effector; determine whether the measured gap distance of the knee joint is equal to a predetermined gap distance; and store, when the measured gap distance is equal to the predetermined gap distance at the measured gap distance, the rotation of the femur as a target femoral implant rotation; and a surgical planning system to plan a position and orientation of a resection of the femur for implantation of a femoral implant at the target femoral implant rotation, wherein the first point on the femur and the first point on the tibia are defined such that, when the distance between the points is equal to the predetermined gap distance, the measured gap distance results in soft tissue balancing. an end effector of a robotic arm to couple to a femur of a knee joint with a soft tissue balancing component that permits the femur to freely rotate while coupled to the end effector; a robotic controller to: cause the robotic arm to apply a pulling force to the femur using the end effector to increase a gap distance between a first point on the femur and first point on a tibia of the knee joint; measure the gap distance between the first point on the femur and the first point on the tibia and a rotation of the femur as the robotic arm applies the pulling force to the femur using the end effector; determine whether the measured gap distance of the knee joint is equal to a predetermined gap distance; and store, when the measured gap distance is equal to the predetermined gap distance at the measured gap distance, the rotation of the femur as a target femoral implant rotation; and cause the robotic arm to apply a pulling force to the femur using the end effector to increase a gap distance between a first point on the femur and first point on a tibia of the knee joint; measure the gap distance between the first point on the femur and the first point on the tibia and a rotation of the femur as the robotic arm applies the pulling force to the femur using the end effector; determine whether the measured gap distance of the knee joint is equal to a predetermined gap distance; and store, when the measured gap distance is equal to the predetermined gap distance at the measured gap distance, the rotation of the femur as a target femoral implant rotation; and a surgical planning system to plan a position and orientation of a resection of the femur for implantation of a femoral implant at the target femoral implant rotation, wherein the first point on the femur and the first point on the tibia are defined such that, when the distance between the points is equal to the predetermined gap distance, the measured gap distance results in soft tissue balancing.