The authors of this study demonstrate a new method for assessing relat
ive rotational alignment of femoral and tibial components in total kne
e arthroplasty. This postoperative method requires only a lateral radi
ograph of the knee in full extension, This technique was demonstrated
with repeated measurements by 2 independent observers to be accurate a
nd reproducible in documenting the rotation of knee implants, This tec
hnique has clinical application in determining the accuracy of contemp
orary alignment techniques, assessing the reliability of anatomic land
marks referenced in implant alignment, and documenting the impact of m
alrotation on the function and longevity of components in total knee a
rthroplasty.