Hallux rigidus is osteoarthritis of the 1st metatarsophalangeal (MTP) joint, causing pain and progressive loss of great toe dorsiflexion, and it is the most common arthritic condition of the foot.
About 2.5% of people over 50 report it. Unlike ankle OA it is usually primary (idiopathic), often bilateral and familial, although it can follow trauma such as turf toe, osteochondral injury, inflammatory arthritis or gout. Hallux limitus describes earlier, painful but partly preserved motion.
Normal 1st MTP motion is about 75° of dorsiflexion, which push-off needs.
The 1st MTP joint lies between the 1st metatarsal head and the base of the proximal phalanx. The plantar plate gives plantar stability, and the 2 sesamoids within flexor hallucis brevis act as a pulley; sesamoid arthrosis develops as the disease advances.
The pathology starts dorsally. A dorsal osteophyte forms on the metatarsal head and blocks dorsiflexion, and cartilage loss begins dorsally where impingement is greatest. While the plantar cartilage is preserved, joint-sparing surgery can work.
At push-off, great toe dorsiflexion tightens the plantar fascia and makes the foot a rigid lever (the windlass mechanism). When it is lost, patients roll off the lateral border of the foot or shorten their stride, causing transfer metatarsalgia under the 2nd and 3rd metatarsal heads.
Think dorsal first in hallux rigidus.
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