A bunion is a firm, fluid-filled pad overlying the inside of the joint at the base of the big toe (metatarsophalangeal joint). The pad (bursa), which may get larger and stick out, can become inflamed and painful. Bunions may run in families, but many result from wearing tight shoes. Nine out of 10 bunions are developed by women. Nine out of 10 women wear shoes that are too small. Tight shoes also can cause other disabling foot problems like corns, calluses and hammertoes.