What are the causes of leg and foot cramps in the middle of the night?

Cramps: If you do not have any circulatory problems, those cramps could be caused by overuse syndrome of the leg and calf muscles as well as the intrinsic muscles in the feet. Skeletal and muscle malfunction while walking can cause many muscles to over work and produce high amounts of lactic acid. Once you stop to rest/go to bed, the lactic muscles trigger the cramping. See a podiatrist for orthoses eval.

Foot cramps: Leg and foot cramps can be caused by many different things such as low potassium to nerve problems to circulation problems. You need some blood work and possible doppler to check for circulation problems unless you already suffer from systemic issues you have not disclosed.