Hello dear, In the absence of any history of wear & tear or injury, muscle cramps & leg pain can be due to: 1. Deficiency of certain nutrients like Iron, Vitamin B 12, Vitamin D, Calcium, etc. which interferes with blood formation & nerve conduction. 2. Decrease in blood sugar levels (Hypoglycemia) 3. Hormonal imbalance like Hypothyroidism. 4. Lack of adequate hydration, proper nutrition & good sleep. 5. Even emotional factors like stress/tension can lead to such symptoms. Investigations like complete blood count, estimation of hemoglobin concentration & blood sugar levels will be helpful in clinching the diagnosis. Wishing you Good Health. Thanks and take care.