Big toe got you down?  It may be hallux rigidus. A stiff and painful big toe can knock you off your feet. Here's what you can do about it.
D001696:Biomechanical Phenomena; D005260:Female; D006214:Hallux / Q000502:physiology; D020859:Hallux Rigidus / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008683:Metatarsophalangeal Joint / Q000502:physiology / Q000601:surgery