I was reading up on a post made by health24.com which suggests that creatine may cause cramp..
Cramp is a tight intense pain that is common in leg muscles and is caused when a muscle contracts and doesn’t relax. Cramps are usually temporary and doesn’t normally lead to serious muscle problems. Some factors that may cause cramp are; poor fitness, exercising at high work loads (overlifting), too little stretching before workouts and creatine (reported by atheletes).
If you do get cramp and it’s severe or occurs regularly or fails to improve with simple treatment, you need to see a doctor.