SAN FRANCISCO — Chondroitin sulfate slows the loss of cartilage in knee osteoarthritis (OA) while soothing the pain, researchers say.

“This is quite significant,” said lead investigator Jean-Pierre Pelletier, MD, of the University of Montreal.

Chondroitin can be found in the connective tissues of humans and animals. Derived from such sources as beef and shark cartilage, it is mostly sold as a nutritional supplement in the United States.

Researchers have long debated its effectiveness in treating OA, a disease in which cartilage loss causes painful friction within the knee joint.

To see how chondroitin could affect patients with OA of the knee, Pelletier’s team studied 194 people with knee OA and inflammation of the synovial membrane in the knee. They followed the participants for two years and divided them into two groups.

The first group took 1200 mg of pharmaceutical-grade chondroitin daily formulated by the Spanish company Bioibérica.

Normally to measure the effectiveness of a drug, researchers compare it to a placebo – a fake drug that is not expected to directly affect the disease. But the researchers did not want any patients to be in pain for the two-year duration of the study.

So they gave the second group 200 mg of Celebrex daily. Celebrex is a prescription pharmaceutical drug designed to selectively suppress an aspect of the inflammatory process with fewer side effects when used long-term. It is often prescribed for the pain of osteoarthritis, but does not affect the cartilage, Pelletier said.

“We felt the present study was necessary in order to establish — using the most recent imaging technology available, quantitative magnetic resonance imaging (qMRI) — whether chondroitin sulfate can truly and effectively reduce the progression of the disease in patients suffering from knee OA,” Pelletier said.

After the initial evaluation, the researchers followed up with participants again at one and two years to look at a number of factors that would indicate the effectiveness of chondroitin.

At all three touchpoints with the participants, the researchers used MRI to detect loss of cartilage, changes in bone marrow legions, and thickening of the synovial membrane in the knee.

Additionally, they evaluated patients for swelling and fluid in the knee and their overall symptoms — collected through the visual analogue scale (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).

When compared with the patients taking Celebrex, those taking chondroitin had less cartilage loss in the whole knee, and especially in the inner half of the knee, after one year and again after two years.

Additionally, there was a decrease in synovial membrane thickness in some of the participants on chondroitin. There was no such change in the Celebrex group.

In both groups, a large number of patients had a marked reduction in swelling and fluid in the knee. Both groups also showed a similar effectiveness at reducing OA symptoms over the course of the study.

Finally, both groups were able to reduce the amount of acetaminophen they took each day, and both experienced a good tolerance to the treatment they were taking.

While these results are promising, Pelletier pointed out that the study only used pharmaceutical-grade chondroitin and results may not be similar for all chondroitin products sold as food supplements. Studies have shown that many food supplements do not contain the ingredients on the label, he said.

He recommends that patients consult with their physicians on the use of such treatment for OA.