Fig. 2

Angle and joint space criteria measured on postoperative weight bearing X-ray 12 months after knee surgery. 2a: MPTA: This is measured by drawing a line in parallel with the tibial joint surface and measuring the medial angle between this line and a line drawn along the long axis of the tibia. Values > 5° from 90° were considered to be malalignment [12, 13]. 2b: PPTS angle: Longitudinal axis of the tibia (LAT, as black line) equals the line passing through two points located in the center of the anterior-posterior width of the tibia at 6 and 10 cm apart on the proximal diaphysis (the two distal green lines). The angle formed between the line perpendicular to the LAT (grey) and the line passing through the highest anterior and posterior points of the tibial plateau (purple) represents the PPTS angle. The slope was defined as positive if the line passing through the highest posterior point of the tibial plateau was below the perpendicular line [14]. 2c: Medial and lateral JSN: Line between midpoints is the long axis of tibial shaft (LATS) (yellow line). Midpoints (white line) of the medial and lateral compartments were identified by using the line between the medial and lateral edges of each compartment of the tibial plateau (green line). Midpoint lines (red lines) were drawn parallel to the LATS through the midpoint of each compartment. The distance between the femoral and tibial intersections was measured (blue line). This is the JSN measurement of each compartment respectively [15]