Bowleg is a condition in which the legs have a gradual or sudden bent due to various reasons. In medical terms we call them varus (bent inwards) or valgus (bent outward).

Normally, on standing both the knees bear equal weight, and within the knee itself the load is borne equally by the inner and outer side. When a person has bowlegs there is increased load on the inner side of the knee more commonly (Varus) or the outer side of the knee (Valgus). This increased loading causes that side to wear out faster and then presents as pain.

Generally the body is able to compensate slight bow in the legs by the action of muscles. But when the bent is beyond a certain limit then the muscles cannot compensate and this results in reduction in the joint space and gradual worsening of the angle.