Walking with outstretched feet, standing at a rest posture, wearing high heels for a long time, sitting cross-legged, kneeling, squatting, etc., will give the knee joint outward force, and this force will pull the lateral collateral ligament of the knee joint For a long time, it will cause the lateral collateral ligament of the knee to relax.
The medial and lateral collateral ligaments of the knee joint are the stable structures of the medial and lateral angles of the knee joint. When the lateral collateral ligament is loose, the greater force of the medial collateral ligament will pull the tibia of the calf to rotate medially, forming a knee varus, that is, an O-leg.