Harvard Health Letter

Special section: Feet: Agonies of the feet: Four common foot problems

Special section: Feet

Agonies of the feet: Four common foot problems

Bunions

illustration of foot with bunion

They develop when the joint formed by the metatarsal and proximal phalanx bones of the big toe fall out of their normal, relatively straight alignment and angle out, creating an outward bulge at the base of the big toe. The bursa that cushions the joint may also get inflamed and enlarge. Often the end of the metatarsal bone becomes larger and misshapen.

Causes. Some people have a natural tendency to develop bunions because the big toe's metatarsal bone is splayed out to begin with. Wear-and-tear and being overweight can splay it out even further. Lack of an arch and overpronation (walking on the inside of your foot) put more weight on the big toe and its metatarsal-phalangeal joint. Jamming feet into narrow shoes puts backward pressure on the big toe, so it buckles out, forming a bunion.

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