Causes of Mechanically Induced Collagen Damage in Articular Cartilage

ABSTRACT: Osteoarthritis (OA) is a multifactorial disease, associated with articular cartilage degeneration and eventually joint destruction. The phases of the disease have been described in detail, and mechanical factors play an important role in the initiation of OA, but many questions remain about its etiology. Swelling of cartilage, one of the earliest signs of damage, is proportional to the amount of collagen damage. This strongly suggests that damage to the collagen network is an early event in cartilagedegeneration.Thegoal of this studywas to determine themechanical cause of early collagen damage in articular cartilage after mechanical overloading. Both the shear strain along the fibrils and the maximum fibril strains were evaluated as possible candidates for causing collagen damage. This evaluation was done by comparing the locations of maximum shear and tensile strains with the locations of initial collagen damage after mechanical overloading in bovine explants as foundusingantibodiesdirected against denatured type II collagen (Col2-3/4M). Collagen damagecould be initiatedbyexcessive shear strainsalong the collagenfibrils, andbyexcessivefibrils strains.The locationsof collagendamageaftermechanical overloadingwerehighlydependent on the cartilage thickness, with thinner cartilage being more susceptible to damage than thicke