Knock-knee and bow-leg alignment is a misalignment in the knee joint. With knock knees, the outer structures are overloaded and with bow legs, the inner structures are overloaded. This overloading can lead to early wear and tear of the joint and thus to osteoarthritis of the knee. However, the knee misalignment often remains unnoticed for a long time without any symptoms. A slight O alignment is normal in infants. A slight X alignment can also be physiological in small children (2 to approx. 5 years old). There are various causes of X and O alignment. Vitamin D deficiency, muscle imbalances, obesity and growth disorders are just a few examples. Foot malpositions, such as fallen arches or hollow feet, are also frequently associated with bowlegs and knock-knees.