Alterations of the Subchondral Bone in Osteoarthritis: Complying with Wolff's Law

Osteoarthritis (OA) is a whole joint disease that is significantly related to abnormal mechanical loads. Subchondral bone alterations, during the evolution course of OA, are considered a reflection of the adaptation of the bone tissue to mechanical loads. However, some of these alterations are taken as a detriment and paradoxical. What are these structure, composition, and mechanical property alterations or mechanical functions for are not quite clear. In this review, we discuss the possibility that these alterations are used for maintaining the joint function. With taking excessive load as a risk factor and under conditions of articular cartilage gradually lose its thickness and its function of evenly distributing the load on the subchondral bone plate, and applying Poroelasticity to bone mechanics; moreover, Boussinesq's pressure bulb theory and bone optimal design principles are utilized. We found that each subchondral bone alteration has its unique mechanical function in resisting loads and maintaining the joint function, and these alterations comply with both bone optimal design principles and Wolff's law within a proper range.