I have been having this issue for a few years and have thought it was nothing to follow up on until now. Occasionally when i sit cross legged for a while or of i stretch my toes upward the muscle in the inside edge of my foot Will cramp up with excruciating pain. When this happens it usually lasts anywhere from 10 seconds to a minute and the muscle will bulge out about half an inch from the side of the arch of my foot causing me to instantly drop what im doing (including myself if i am standing) the pain lasts until the muscles relaxes and moves back into its normal position. I have spent hours searching for an answer but i could not find any similar cases. I cannot afford the time off work to see a doctor, so if you have any idea what it is please help