Cramping of the feet and lower legs can be due to a wide variety of conditions. The most common cause of foot and leg cramps is simple overactivity of muscle, which results in overstimulation of muscle fibers. The overstimulated fibers will contract, leading to cramping. This process can be due to fatigue from new or strenuous activity, or it may be due to fatigue associated with one's foot structure. For example, participating in a new exercise without proper training, walking excessively on vacation, or having flat feet that fatigue easily can lead to muscle cramping. Dehydration plays a big role in this cause as well, often predisposing someone to develop cramps in addition to overactivity.
Muscle cramps can also develop when there is nerve disease present. Nerves tell muscles when to contract based on instructions from the brain, either conscious or subconscious. When the nerves are diseased, muscles can contract at abnormal times without the brain‘s input. This condition is seen in those with lower back arthritis and spinal nerve pinching, those with diabetes, and those with other leg-based nerve diseases.
Poor circulation can also lead to a sensation of cramping if the lack of oxygen affects muscle tissue or the nerve tissue that controls muscle contractions. The pain from this can be quite severe and will worsen if one is at rest or is elevating the leg.
Other causes of muscle cramping include abnormalities of muscle-aiding nutrients like calcium, magnesium, and potassium (often mistakenly assumed to be more common than they really are), certain medications like steroids, water pills, and cholesterol drugs, neuromuscular diseases, as well as injuries to the muscle itself.
The treatment of muscle cramps generally involves stretching or massaging the muscle involved, which essentially helps it to relax. Applying heat to the cramped area can also help. Changing one's exercise routine, performing pre-activity stretching, and wearing proper shoes (and foot inserts if needed) for the specific activity is often necessary to prevent the development of cramping. If the cramping is due to a nutrient deficiency, nerve disease, circulatory issue, or medication, each of those individual factors needs to be addressed to either prevent or reduce the cramping as stretching may be insufficient in those cases.