Most of the time, no apparent cause for night leg cramps can be identified. In general, night leg cramps are likely to be related to muscle fatigue and nerve problems. The risk of having night leg cramps increases with age. Pregnant women also have a higher likelihood of having night leg cramps. Several conditions, such as kidney failure and diabetic nerve damage, are known to cause night leg cramps. But if you have one of these, you're most likely aware of it and have symptoms other than night leg cramps.