The role of crystals in osteoarthritis

Calcium-containing crystals, such as calcium pyrophosphate dihydrate and ba sic calcium phosphate, have profound in vitro biologic effects. They promot e synovial hyperplasia and synthesis of metalloproteases able to degrade ca rtilage matrix. Clinical observations support the thesis that these in vitr o effects also occur in vivo. Prospects for successful interventions in the crystal deposition diseases depend upon better understanding of the mechan isms of crystal formation and activation pathways that lead to their biolog ic effects.