Fig. 1

Anteroposterior Knee X-rays of a left knee showing the different joint line measure techniques. In the Weber 1 method, the angle (alpha) between a line that goes through the most distal point of both femoral condyles (JL) and the lateral femoral cortex (a) is obtained in the pre-operative x ray (a). Then (alpha) is reproduced in the post-operative x ray (b) with the lateral femoral cortex and the non-operative femoral condyle as reference. The variation in joint line is then measured. In the Weber 2 method the angle (beta) is obtained in the pre-operative x ray (c) between a line that goes through the most distal point of both femoral condyles (JL) and the line B that goes from the most proximal point of the intercondylar notch and the center of a line 10 cm proximal to it (c). Then the angle is reproduced in the post-operative x ray (d) with line B and the non-operative condyle as reference. The variation in joint line is then measured. In the Iacono method, the distance (AT) between the most proximal point of the Adductor Tubercle perpendicular to a line that goes through the most distal point of both femoral condyles (JL) (e) is compared to the same distance in the post-operative x ray (f). The difference between both is the variation in joint line