A hallux abducto valgus deformity, commonly called a bunion, is a deformity characterized by lateral deviation of the great toe, often erroneously described as an enlargement of bone or tissue around the joint at the head of the big toe.

The term “hallux” or “hallux abducto-valgus”, where “hallux” refers to the great toe, “valgus” refers to the abnormal angulation of the great toe commonly associated with bunion anomalies, and “abductus/-o” refers to the abnormal drifting or inward leaning of the great toe towards the second toe, which is also commonly associated with bunions. It is important to state that “hallux abducto” refers to the motion the great toe moves away from the body’s midline. Deformities of the lower extremity are usually named in accordance to the body’s midline, or the line bisecting the body longitudinally into two halves. In more severe cases, the hallux continuing in the abductus fashion eventually either overlaps or underlaps subsequent lesser (small) toes especially the second (adjacent toe).