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Oiling an Arthritic Joint? Part 1

by Jose Fernando Syquia, MD, FPOA

When we think of oil, we think of a very slippery substance that makes motion between two surfaces very smooth. Thus, when one develops arthritis and is told that his joint is damaged and not functioning properly, an idea that pops into the mind is whether an oil-like substance could be put into the joint to make it move smoothly again. But does such a substance exist?

Our joint does have an oil-like substance that greatly contributes to its very smooth motion. This substance is called synovial fluid and the main component of this fluid is hyaluronic acid. With osteoarthritis, the concentration and molecular weight of hyaluronic acid is decreased, leading to a loss in the viscosity of the synovial fluid. You could think of it as replacing the oil in your car engine with water – that is what happens to a joint with osteoarthritis.

The injection of hyaluronic acid into a joint is called viscosupplementation. Through this procedure, one is able to supplement synovial fluid viscosity that was diminished because of osteoarthritis. Hyaluronic acid also decreases the inflammation of the joint lining (called synovium) and this is believed to decrease damage to the cartilage brought about by the byproducts of inflammation. Finally, hyaluronic acid decreases joint pain due to its anti-inflammatory properties and its direct inhibition of pain receptors. But how effective is viscosupplementation?

As early as 1982, in a study published in the International Journal of Clinical Pharmacology and Therapeutics (Therapeutic Effect of Intra-articular Injection of High Molecular Weight Hyaluronic Acid on Osteoarthrits of the Knee), Namiki, et. al. demonstrated the beneficial effects of hyaluronic acid on 32 of 45 knees that were treated. Since then, several studies have come out that have shown how effective this form of treatment is in controlling the symptoms of osteoarthritis. However, there were also studies that seemed to contradict these favorable findings.

In 2008, the American Academy of Orthopaedic Surgeons (AAOS) stated that they could not recommend for or against viscosupplementation for patients with mild to moderate knee osteoarthritis. They based their conclusion mainly on a report from the Agency for Healthcare Research and Quality that looked at 42 trials in six meta-analyses that concluded that although viscosupplementation generally showed positive effects, the results could have been influenced by trial quality, potential publication bias, and unclear clinical significance or importance.

Rutjes, et. al., in a 2012 article published in the Annals of Internal Medicine (Viscosupplementation for Osteoarthritis of the Knee: A Systematic Review and Meta-Analysis), concluded that the benefits of viscosupplementation for pain and function in patients with knee osteoarthritis was minimal or non-existent.  Their meta-analysis involved 89 trials with 12,667 patients. The study actually showed that viscosupplementation moderately reduced pain of osteoarthritis and moderately improved function; however, the risk of publication bias appeared great since studies with large samples and studies that were not published showed smaller positive effects.

A year later, in 2013, the AAOS came out with their updated guidelines on the treatment of knee osteoarthritis. They stated that they cannot recommend using hyaluronic acid for patients with symptomatic osteoarthritis of the knee. Although the review found that there was a statistically significant improvement in pain, function, and stiffness, none of the improvements met the “minimum clinically important improvement” thresholds.

To be continued…



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