An orthopedic instrument for knee arthroplasty includes an anterior-posterior sizer assembly, a tensor assembly and a rotation mechanism. The sizer assembly includes a stylus, a sizer body including medial and lateral posterior feet extending substantially perpendicularly from the sizer body, and a sizer slider that can slide relative to the sizer body along a medial-lateral direction relative to a patient's knee. The tensor assembly includes a tensor frame having a central portion, medial and lateral wings extending at an angle from the central portion, and medial and lateral posterior feet extending substantially perpendicularly to the central portion. The rotation mechanism includes a portion coupled to the tensor frame of the tensor assembly and a portion coupled to the sizer body. The rotation mechanism is configured to rotate the medial and lateral posterior feet of the sizer body relative to the tensor frame toward a lateral side of the patient's knee.