Rickets Pathophysiology

Rickets is a disease that directly results from a lack of Vitamin D and the improper mineral absorption that comes from response to that. If not enough Vitamin D is ingested, calcium and phosphorus cannot be absorbed. These minerals are crucial in the formation and maintenance of healthy and strong bones. Low Vitamin D levels leads to low calcium absorption in the intestines. In order to make up for this, the body will increase levels of Parathyroid Hormone (or PTH) which signals the body to increase levels of calcium. The body will them begin to reabsorb calcium from its own bones.  A disruption in the homeostasis (or equilibrium) of calcium and phosphorus causes poor calcification (or accumulation of calcium) of the cartilage in growing long bones such as the femur. This is what contributes to the bowing of the legs. The bones are weaker and less dense because not enough calcium has been brought together. Thus, it is more likely for the bones to bend.  

These legs are affected by rickets, and display bowed legs.

Image source

Additionally, rickets can cause the widening of wrist or the splaying of bones. The bones may be widening in attempt to compensate in size for what they lack in strength. This doesn’t do much to help however, bone stability is not enhanced.

For more information, please read:

http://emedicine.medscape.com/article/985510-overview#a5
                                   or
http://www.uptodate.com/contents/overview-of-rickets-in-children