bunion medical definition
The medical definition of a bunion is a deformity of the big toe joint that results in a prominent bump on the inner side of the foot at the base of the big toe. This bump is formed by the displacement of the big toe joint, known as the metatarsophalangeal (MTP) joint, and caused by the misalignment of the bones in the big toe. The big toe is pushed towards the other toes, causing the head of the first metatarsal bone (the bone that connects to the big toe) to protrude out of place. This creates a bunion and the joint becomes enlarged and inflamed.