The common bunion is a localized area of enlargement of the inner portion of the joint at the base of the big toe. The enlargement actually represents a misalignment of the big toe joint (metatarsal phalangeal joint) and, in some cases, additional bone formation. The misalignment causes the big toe to point outward (medically termed hallux valgus deformity) toward the smaller toes. This deformity is progressive and will increase with time. The enlarged joint at the base of the big toe (the first metatarsophalangeal joint, or MTP joint) can become inflamed with redness, tenderness, and pain. A small fluid-filled sac (bursa) adjacent to the joint can also become inflamed (bursitis), leading to additional swelling, redness, and pain. A more deep joint pain may occur as localized arthritis develops in later stages of the deformity.
A less common bunion is located at the joint at the base of the smallest (fifth) toe. This bunion is sometimes referred to as a tailor's bunion or bunionette.