A bunion is a bony protrusion that develops on the joint at the base of the big toe. It is caused by a misalignment of the bones in the big toe joint, where the big toe starts to point towards the second toe, and the joint at the base of the big toe becomes prominent. This misalignment causes the bones to rub together, leading to inflammation and pain. It can also cause a callus to form on the skin over the bunion, and it can make it difficult to find shoes that fit comfortably. Bunions can also change the shape of the foot, making it difficult to walk. Bunions are a common condition, and can be caused by a variety of factors including genetics, foot mechanics, trauma, ill-fitting shoes, and certain medical conditions.