An orthopaedic surgical instrument system comprising: a tibial base trial including a plate configured to be positioned on a proximal end of a patient's tibia and a post extending outwardly from a superior surface of the plate; a hinged tibial insert trial including (i) an inferior surface configured to confront the superior surface of the plate, (ii) a pair of curved surfaces (104, 106) positioned opposite the inferior surface, (iii) a spine positioned between the pair of curved surfaces (104, 106), (iv) a housing hingedly coupled to the spine and including a button mechanism having an elongated plunger pin, and (v) a central opening defined in the inferior surface; a post adapter sized to be positioned in the central opening defined in the hinged tibial insert trial, the post adapter including an outer wall and an aperture defined in the outer wall and sized to receive the post of the tibial base trial; and a femoral component including (i) a pair of curved surfaces (198, 200) configured to confront the pair of curved surfaces (104, 106) of the hinged tibial insert trial, (ii) an anterior flange positioned between the pair of curved surfaces (198, 200), (iii) a femoral box defined between the pair of curved surfaces (198, 200) and configured to receive the housing of the hinged tibial insert trial, and (iv) a pocket defined in an inner wall of the anterior flange and configured to receive a first end of the elongated plunger pin; wherein the housing comprises a medial wall, a lateral wall, and an anterior wall, the housing having a bore defined in the anterior wall; the first end of the plunger pin selectively extends through the bore in the anterior wall; and the button mechanism comprises a spring configured to bias the first end of the plunger pin to extend through the bore; wherein the medial wall, the lateral wall, and the anterior wall cooperate to define a button chamber accessible through the bore in the anterior wall, and wherein the button mechanism is positioned within the button chamber; and the button mechanism comprises a button plate coupled to the plunger pin and extending through an inferior opening in the button chamber; and wherein the button mechanism is operable to retract the first end of the elongated plunger pin within the housing. a tibial base trial including a plate configured to be positioned on a proximal end of a patient's tibia and a post extending outwardly from a superior surface of the plate; a hinged tibial insert trial including (i) an inferior surface configured to confront the superior surface of the plate, (ii) a pair of curved surfaces (104, 106) positioned opposite the inferior surface, (iii) a spine positioned between the pair of curved surfaces (104, 106), (iv) a housing hingedly coupled to the spine and including a button mechanism having an elongated plunger pin, and (v) a central opening defined in the inferior surface; a post adapter sized to be positioned in the central opening defined in the hinged tibial insert trial, the post adapter including an outer wall and an aperture defined in the outer wall and sized to receive the post of the tibial base trial; and a femoral component including (i) a pair of curved surfaces (198, 200) configured to confront the pair of curved surfaces (104, 106) of the hinged tibial insert trial, (ii) an anterior flange positioned between the pair of curved surfaces (198, 200), (iii) a femoral box defined between the pair of curved surfaces (198, 200) and configured to receive the housing of the hinged tibial insert trial, and (iv) a pocket defined in an inner wall of the anterior flange and configured to receive a first end of the elongated plunger pin; wherein the housing comprises a medial wall, a lateral wall, and an anterior wall, the housing having a bore defined in the anterior wall; the first end of the plunger pin selectively extends through the bore in the anterior wall; and the button mechanism comprises a spring configured to bias the first end of the plunger pin to extend through the bore; wherein the medial wall, the lateral wall, and the anterior wall cooperate to define a button chamber accessible through the bore in the anterior wall, and wherein the button mechanism is positioned within the button chamber; and the button mechanism comprises a button plate coupled to the plunger pin and extending through an inferior opening in the button chamber; and wherein the button mechanism is operable to retract the first end of the elongated plunger pin within the housing.