**5. Pathology and pathogenesis**

OA is a heterogenous spectrum of clinical condition affecting mostly joints. No one mechanism explains the various processes seen in the joint of OA. Factors including inflammation, genetic, injury or trauma and joint mechanics have all been implicated in the pathophysiology of OA. Each joint response is a balance of the anabolic and catabolic factors acting in combination with both the extrinsic and intrisic factors.

Summary of the mechanisms suggested for the pathogenesis of OA are:

• *Matrix loss:* Metalloproteinases (MMPs) such as stromelysin and collagenase which are secreted by the chondrocytes catalyses the degradation of both collagen and proteoglycans resulting in matrix loss


Fig. 2. Different factors that influence OA process.


Table 1. Stages of OA (Martel-Pelletier, 2004)
