Abstract: A tibial resector guide having an angularly adjustable head controlled by a thumb actuated slide mechanism. The head may be positioned in a plurality of predetermined angular orientations in the anterior-posterior plane. The cutting head guide includes angled side walls which permit the guide to have a narrow aperture yet allow the saw blade to completely pass through the tibia. Further, the tibial resector of this invention includes a telescoping rod and a length adjustment mechanism adjacent the head for providing small height adjustments for positioning the head. The length adjustment member includes an enlarged thumb wheel to ease operation. A pinning platform is connected to the adjustment member such that it is shiftable with the adjustment member relative to the guide head. The pinning platform permits the surgeon to pin the upper end of the instrument to the patient's leg preventing movement of the instrument during resection.