In vitro models for investigation of the effects of acute mechanical injury on cartilage

Traumatic injury to a joint is known to increase the risk for the developme nt of secondary osteoarthritis, but it is unclear how this process occurs. The existence of such a discrete event that can lead to an increased risk o f osteoarthritis has spurred interest in developing in vitro models of trau matic joint injury. The current authors review some of the recent insights gained from these model systems into the pathogenesis of osteoarthritis, in cluding the evidence for an initial, irreversible insult to chondrocytes du ring mechanical injury, the occurrence of apoptotic chondrocyte death, and attempts to identify the effects of trauma on chondrocyte metabolic respons e. Results also are presented from the authors' ongoing studies of the degr adative pathways initiated by traumatic mechanical loads, the mechanism by which chondrocytes are affected during compression, and possible contributi ons of the joint capsule to posttraumatic cartilage degradation.