Tibial trial implant (1, 100) for use in a knee joint replacement operation, having - a lower part (2, 102), which is provided for tibial fixation, - an upper part (3, 103) arranged above the lower part (2, 102) in the height direction and having a glide face (5, 105) which is arranged on an upper side and which is provided for gliding interaction with a femoral component, - a height adjustment mechanism (E, E'), which is operatively connected to the upper part (3, 103) and the lower part (2, 102) and by means of which the upper part (3, 103) can be guided displaceably relative to the lower part (2, 102) in the height direction between - a first adjustment position, in which the glide face (5, 105) is positioned at a first height above the lower part (2, 102), and - a second adjustment position, in which the glide face (5, 105) is positioned at a second height above the lower part (2, 102), - wherein the height adjustment mechanism (E, E') has a cam gear with at least one drive wheel (6a, 6b, 106a, 106b), which is mounted rotatably on the lower part (2, 102) about a first rotation axis (8a, 8b) oriented parallel to the height direction and has a control cam (9a, 9b, 109a, 109b) rising in the height direction, and with at least one driven element (7a, 7b, 107a, 107b), which is firmly connected to the upper part (3, 103) and has a supporting section (10a, 10b, 110a, 110b) glidingly supported on the control cam (9a, 9b, 109a, 109b), as a result of which the upper part (3, 103) can be displaced, by means of a rotational movement of the drive wheel (6a, 6b, 106a, 106b), between the first adjustment position and the second adjustment position, - characterized in that a scale display is formed between the lower part and the at least one drive wheel (6a, 6b), which scale display has a reading element and a scale and allows reading of the adjustment position of the upper part and/or of the height (H1, H2) of the glide face, or - in that the at least one drive wheel (106a, 106b) is coupled so as to transmit movement to at least one display wheel (130a, 130b) which is rotationally mounted on the lower part, the display wheel (130a, 130b) having a scale (S') which allows reading of the adjustment position of the upper part and/or of the height of the glide face. - a lower part (2, 102), which is provided for tibial fixation, - an upper part (3, 103) arranged above the lower part (2, 102) in the height direction and having a glide face (5, 105) which is arranged on an upper side and which is provided for gliding interaction with a femoral component, - a height adjustment mechanism (E, E'), which is operatively connected to the upper part (3, 103) and the lower part (2, 102) and by means of which the upper part (3, 103) can be guided displaceably relative to the lower part (2, 102) in the height direction between - a first adjustment position, in which the glide face (5, 105) is positioned at a first height above the lower part (2, 102), and - a second adjustment position, in which the glide face (5, 105) is positioned at a second height above the lower part (2, 102), - wherein the height adjustment mechanism (E, E') has a cam gear with at least one drive wheel (6a, 6b, 106a, 106b), which is mounted rotatably on the lower part (2, 102) about a first rotation axis (8a, 8b) oriented parallel to the height direction and has a control cam (9a, 9b, 109a, 109b) rising in the height direction, and with at least one driven element (7a, 7b, 107a, 107b), which is firmly connected to the upper part (3, 103) and has a supporting section (10a, 10b, 110a, 110b) glidingly supported on the control cam (9a, 9b, 109a, 109b), as a result of which the upper part (3, 103) can be displaced, by means of a rotational movement of the drive wheel (6a, 6b, 106a, 106b), between the first adjustment position and the second adjustment position, - characterized in that a scale display is formed between the lower part and the at least one drive wheel (6a, 6b), which scale display has a reading element and a scale and allows reading of the adjustment position of the upper part and/or of the height (H1, H2) of the glide face, or - in that the at least one drive wheel (106a, 106b) is coupled so as to transmit movement to at least one display wheel (130a, 130b) which is rotationally mounted on the lower part, the display wheel (130a, 130b) having a scale (S') which allows reading of the adjustment position of the upper part and/or of the height of the glide face.