Rickets is a childhood disease that's caused by a lack of vitamin D. Rickets results in malformation of the bones.
There are many diseases that result from poor nutrition, and rickets is one of these. If a child doesn't get enough vitamin D through food and sunlight, his bones can become curved, soft, or brittle. Someone who is bowlegged — whose legs curve out — may have had rickets as a child. Rickets is less common these days, due to better nutrition. The word rickets is thought to be a version of the Greek word for "inflammation of the spine," rhachitis.