The Knee Bends Only Forward, and Rising from a Kneel
Why the knee joint has no sideways play, and the sequence by which a man stands up
The text explains that the leg below the knee cannot turn without the thigh, because the knee joint permits only forward-and-backward motion, not lateral: were it as free as the shoulder or hip, the legs would twist sideways and be useless. The knee also bends only forward and never backward, for a backward bend would make it impossible to rise from kneeling. Leonardo then describes that rising in detail: the weight is loaded onto one knee and off the other, the freed foot is planted flat, the hand presses on the knee, and the arm, chest, head, and thigh extend together until the man stands upright. A final heading opens the chapter on the folds of the flesh. The page is entirely text.
On this page
The knee joint allows no lateral motion
The knee-bone is set within and joined to the leg bone so that the joint moves only forward and backward, as walking and kneeling require, and never sideways. If it were as free as the shoulder or the hip, the legs would always be twisted; and it bends only forward, never backward.
How a man rises from kneeling
In standing up from a kneel, the torso's load is placed on one knee and taken off the other, so that the freed leg easily lifts its knee and plants the sole flat on the ground. The whole weight is then rendered onto that foot, the hand pressing on the knee, and the arm extends to carry chest and head upward while the thigh straightens, until the man stands upright and lifts the other leg.