Hallux rigidity is when the big toe (the hallux) joint is more rigid than it should be. As the joint gets stiffer, it becomes more painful and affects the way you walk. The most common cause is osteoarthritis and is almost always painful. Treatment is typically directed at medications. https://podiatryfaq.com/knowledge-base/what-is-the-difference-between-hallux-rigidus-and-hallux-valgus/