Talonavicular coalition is one of the less common subtypes of tarsal coalition, the most commons being talocalcaneal coalition and calcaneonavicular coalition. As with other forms of coalition it can be osseous, cartilaginous or fibrous.
Uni-or bilateral. Most patients are asymptomatic or present foot pain.
Mushroom sign: the contours of the bone fusion mimic the shape of a mushroom.
Loss of the talar-scaphoid joint line at the level of Chopart's joint.