Research recently presented at the AVS 62nd International Symposium and Exhibition, in San Jose, USA, suggested that exercise could help been prevent knee osteoarthritis.

Osteoarthritis is a degenerative bone disease resulting from a reduction in the cartilage, leading to an increase in friction.

Cartilage is a firm, rubbery material covering the ends of the bones in the knee joint. It reduces friction in the joint and acts as a “shock absorber.”

When cartilage becomes damaged or deteriorates, it limits the knee’s normal movement and can cause significant pain, and eventually the need for knee replacement surgery.

About 80% of the volume of cartilage tissue is made up of synovial fluid. This fluid is needed to support weight and lubricate joint surfaces. The loss of synovial fluid that causes the decrease in cartilage thickness, increase in friction, bone degradation and joint pain of osteoarthritis.

Now a research team from the Mechanical Engineering Department at the University of Delaware has proposed a mechanism that may explain how motion can cause cartilage to reabsorb fluid that leaks out over time.

The team tested their theory that the reabsorption process was driven by hydrodynamic pressurization, which occurs when the relative motion of 2 surfaces causes fluid between them to accelerate in the shape of a triangular wedge.

By modeling joint movement using cartilage samples, the team demonstrated that with increased motion—ie, typical walking speed—the fluid lost to deflation was counteracted by fluid regained through pressurization. The conclusion, according to lead researcher David Burris, PhD, is that “It is activity itself that combats the natural deflation process associated with interstitial lubrication.”

For decades opinion has varied about whether it is better to rest or to exercise an arthritic joint. Common sense might suggest rest, limit the pain and inflammation and preserve the joint. The obvious price paid for this is the very real risk of a stiff joint with weakened surrounding muscles making eventual rehabilitation much more difficult.

This paper adds science to that existing opinion. We know that progressive loss of articular cartilage and synovial fluid are amongst the most damaging factors in the progression of arthritis. The capsule of the joint is porous, allowing normally lubricating synovial fluid to escape from the joint faster than it can be replaced. But if the joint is kept moving by muscular activity the pressure in the tissues surrounding the joint helps to drive fluid back into the joint.

Anyone with a painful inflamed joint will feel the need to rest it, and in the early acute stage this is essential. But increasingly the evidence is that as soon as it becomes possible movement will preserve function and we now learn help to prevent further deterioration in structure too. Compelling evidence.