Hallux rigidus is a condition where the big toe (the hallux) joint is more rigid than it should be. As the joint gets stiffer, it can become more painful and impairs the way you walk. The primary cause is osteoarthritis and is almost always painful. Treatment is typically directed at pharmacological interventions. https://podiatryfaq.com/knowledge-base/what-is-the-difference-between-hallux-rigidus-and-hallux-valgus/