Fig. 3

A diagrammatic representation of different alignment parameters based on the knee society total knee arthroplasty roentgenographic evaluation and scoring system24. The coronal tibiofemoral mechanical angle is the angle resulting from drawing a line from the centre of the femoral head down to centre of the ankle through the centre of the knee (a)—ideally 180°. The coronal femoral angle cFA (b)—ideally 96°—and coronal tibial angle cTA (c)—ideally 90°—are the angles between the components’ coronal axes (the line connecting the femoral components most distal condyles and the line along the horizontal tibial plate) and the bones’ coronal anatomical axes (line which bisects the medullary canal of the femur and tibia respectively). The coronal tibiofemoral anatomical angle is a combination of the coronal anatomical femoral axis and coronal anatomical tibial axis (d). The sagittal femoral sFA (e)—ideally 90°—and sagittal tibial sTA (f)— ideally between 83 and 90°—angles are the angles between the components’ sagittal axes (horizontal line perpendicular to the femoral component peg and line along the horizontal tibial plate) and the anatomical sagittal bones’ axes (line which bisects the medullary canal of the femur and tibia respectively). The axial femoral (aFRA) (g)—ideally 0°—and axial tibial—ideally within 15°—(aTRA) (h) angles are the angles between the components’ axial axes (line through the centre of the femoral pegs and the line through the most posterior points of the tibial plate on axial views respectively) and the bones’ axial axes (surgical epicondylar femoral axis and the tibial tuberosity axis respectively). The combined components axial (aCRA) rotational alignment angles—ideally 0°—is the angle between the components axial axes