A, With knee flexed to 90 degrees for classic anterior drawer sign, medial meniscus, being attached to tibia, abuts against acutely convexed surface of medial femoral condyle and has “doorstop” effect, preventing or hindering anterior translation of tibia. B, With knee extended, relationships are changed. Comparatively flat weight-bearing surface of femur does not obstruct forward motion of meniscus and tibia when anterior stress is applied.