The Science of Hallux Rigidus

Hallux rigidus represents degenerative arthritis of the first metatarsophalangeal joint, characterized by progressive cartilage destruction and osteophyte formation. The condition typically begins with articular cartilage damage on the dorsal aspect of the metatarsal head, where repetitive impingement occurs during the terminal stance phase of gait. Initial cartilage fibrillation progresses to full-thickness defects, exposing underlying subchondral bone. The body's attempt to stabilize the damaged joint results in osteophyte formation, particularly prominent dorsally. These bone spurs create a mechanical block to dorsiflexion, establishing a vicious cycle where restricted motion leads to further impingement and accelerated joint destruction. The synovium becomes chronically inflamed due to cartilage debris and mechanical irritation, producing inflammatory mediators that perpetuate joint destruction. Subchondral bone undergoes sclerotic changes and cyst formation as load distribution becomes increasingly abnormal across the damaged joint surfaces. As the condition progresses, the joint space narrows significantly, and the normal congruent relationship between the metatarsal head and proximal phalanx is lost. Advanced stages demonstrate near-complete loss of dorsiflexion, with the joint essentially fused in a plantar flexed position. This functional ankylosis severely compromises the windlass mechanism and normal push-off mechanics during gait.