Crystal arthritis

Many different crystal types can form in the body and potentially cause acute synovitis, chronic arthropathy, or periarticular syndromes. The most common and clinically relevant crystals are monosodium urate, the causative agent in gout, and calcium pyrophosphate, both of which commonly affect the foot and ankle. Foot involvement, particularly the first metatarsophalangeal joint, is the clinical hallmark of gout.