An Engineer's View of Activity and Knee Health

24 October 2015
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24 October 2015, Comments: Comments Off on An Engineer’s View of Activity and Knee Health

It is well known that exercise and increased activity results in decreased pain and increased function in patients with knee osteoarthritis. It makes sense: more activity and exercises keep muscles, tendon, and ligaments strong, reducing the stress on the joints. But, now, with a paper entitled: “Tribological Rehydration of Cartilage: a New Insight into an old Problem”, a research team from the Department of Mechanical Engineering at the University of Delaware proposes another mechanism of how the mechanical loading and unloading of the joint helps the cartilage inside the knee joint stay healthy. And, is all about cartilage deflation.

Joint cartilage, which is essential for the knee joint’s lubrication and weight bearing capacity, is mostly fluid. Over time that fluid leaks out decreasing the cartilage ability to function, and leading to degradation of the joint, the hallmark of osteoarthritis. That constant fluid leakage is called cartilage deflation.

Whenever two surfaces with fluid in between (like in the knee) move relative to each other, there is an acceleration and an increase in the pressure of the fluid, a phenomenon called hydrodynamic pressurization. The research team tested their theory that the hydrodynamic pressurization caused a reabsorption of the fluid into the cartilage. They created a model of the knee joint and using cartilage samples demonstrated that with increased motion, like walking at normal speed, the fluid lost to deflation was counteracted by fluid regained through pressurization. The conclusion of the researchers was that “activity combats the natural deflation process associated with interstitial lubrication.”

Recalling my engineering background I get excited to read about the mechanical reasons for activity helping our joints. But, even when it may be hard to completely understand the engineering jargon, we can understand this: exercise and activity helps arthritic joints stay healthier.

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