Fig. 4

Schematic illustration of radiographic measurement of medial and lateral joint line difference. Schematic illustration of a left femur with measurement of lateral distal femoral angle (LDFA) and adductor tubercle joint line distance (ATJL) (a). Preoperative (b) and postoperative distal femur (c). Preoperative LDFA (dashed) and ATJL (continuous) illustrated by red lines in (b and c). Green line shows postoperative joint line and perpendicular distance from most distal medial and lateral points to preoperative joint line. 1.) Measurement of preoperative LDFA in °, 2.) measurement of preoperative ATJL in mm as perpendicular distance from the adductor tubercle and the preoperative joint line (≜ LDFA), 3.) reconstruction of the preoperative LDFA and ATJL in the postoperative radiograph and 4.) measurement of the medial (a, mJLD) and lateral (b, lJLD) distance between the most distal point and the preoperative joint line. Example measurement (d) of the medial and lateral joint line alteration including example values of the ATJL, LDFA, mJLD and lJLD