Hallux rigidus is a condition where the big toe (the hallux) joint is more rigid than it should be. As the joint becomes stiffer, it becomes more painful and impairs the way you walk. The primary cause is arthritis of the bones and is almost always painful. Treatment is usually directed at medications. https://podiatryfaq.com/knowledge-base/what-is-the-difference-between-hallux-rigidus-and-hallux-valgus/