Osteoarthritis.

Causes and effects

Causes

It is difficult to determine the initial event that leads to the onset of OA. Nonetheless, all hypotheses associate the OA changes to the mechanical overloading of the joints.

"Wear and tear" is a widely accepted explanation of the cause of OA. It should be noted that OA is the result of an interlocking pathophysiologic malfunction of cartilage and bone metabolism. Interpreting "wear and tear" of the joints in OA from a biomechanic perspective allows patients to understand how OA differs from age-associated degeneration and overuse of the joints. There are ways to reduce the OA "wear and tear" effects which include weight control, muscle strengthening exercises, and increased proprioception accuracy.

It is a common view that OA begins as a fibrillation of articular cartilage, a focal fine roughening of the surface of articular cartilage, that eventually leads to secondary remodeling of the bony components of the joint (48). Remodeling refers to the resorption and formation of bone tissues under the influence of mechanical loading history on the joints.

An alternative hypothesis suggests that OA originates from the stiffness of subchondral bone. Normally it is the bone, not the cartilage, that absorbs most of the impact forces on the extremities. This "stiff bone" hypothesis suggests that mechanical overloading on the joints may result in microfractures in subchondral bones underlying the articular cartilage. The repair of the fractures leads to a net local increase of the stiffness of the bone. The "stiff bone" provides less cushion for the overlying cartilage and thus forces the cartilage to absorb a greater share of the impact energy. The repartition of forces eventually leads to the degeneration of the articular cartilage. The relationship between cartilaginous and bony changes in OA is very complex and intertwined.

A third, and less established hypothesis associates proprioceptive impairment with knee OA. Proprioception refers to the conscious and unconscious perception of joint position and movement. Accurate proprioception is critical to maintain joint stability under dynamic conditions. Joint stability is important to prevent the wear and tear from mechanical forces on the extremities.

How useful was this page or article? This article is rated out of 5 stars (986 ratings). Not useful at all Not very useful Useful Very useful Extremely useful