Vitamin D is formed in the skin when it is exposed to sunlight.
It may also be obtained from some foods, such as fish and eggs. Lack of vitamin D affects the kidneys and disrupts the calcium and phosphorus metabolism in the body. This in turn affects the deposition of calcium in the bones, resulting in deformity. If the condition continues, the ends of the long bones become enlarged. When the infant starts to walk, the legs may bend, resulting in either bowlegs or knock-knees.