It may be lack of posassium, however the primary cause of a "charlie horse" in the foot is lack of circulating calcium. The co-factor is often low levels of vitamin D-3. Because there are no contraindications try 5,000 IU of vitamin D3 and a couple of glasses of milk a day.
Hi there. The various causes of foot cramps or tightening or painful contraction in the middle of foot are an over exerted foot poor foot circulation, lack of potassium, dehydration, pinched nerves due to electrical impulse from brain not reaching the muscles, alcohol or tobacco use, nutritional deficiency, etc. sciatica has been the previous culprit causing pain in back and thigh and leg cramps. This could be pinched nerve in the leg or foot. treatment would include holding the foot slowly in position where the cramp disappears, NSAIDs to relieve the cramp, foot elevation to waist level, soak in warm water, moist heat, wrap in elastic bandage, bed rest to hasten healing, and a orthopaedician consultation followed by a neurologist’s office visit. Hope this helps. Take care.
Forgot to mention that i have taken meds, 2 epidural shots, physical therapy, acupuncture and a lot of stretching.