Injury or surgery can reduce joint lubrication, which makes the cartilage and bone surfaces scrape against each other with more friction, leading to lasting damage. But rapidly injecting the joint with a particular blend of naturally occurring joint substances can help restore healthy lubrication in the synovial fluid, according to researchers in Colorado and California.

In a recent study, a standard dose of combined hyaluronan (hyaluronic acid), sodium chondroitin sulfate, and N-acetyl-d-glucosamine (HCSG) injected into osteoarthritic joints led to fewer changes indicative of joint problems, compared to horses that did not receive HCSG, said David Frisbie, DVM, PhD, Dipl. ACVS, ACVSMR, professor of equine surgery at Colorado State University’s (CSU) Equine Orthopaedic Research Center, in Fort Collins.

“This certainly gives some credence to the use of hyaluronic acid and related biopolymers in the joint to reestablish more normal lubrication in the joint environment,” Frisbie said.

Frisbie and his fellow researchers worked with 16 young, healthy study horses between 2 and 5 years old. They surgically induced osteoarthritis in one knee of each horse by creating an osteochondral fragment with bone debris in the joint. The horse’s other knee either underwent sham surgery (surgery without inducing osteoarthritis) or no surgery. Among the knee joints with induced osteoarthritis, eight received an HCSG injection directly into the joint just after surgery and a second two weeks later. The other eight received saline injections on the same timetable.

The researchers aspirated synovial fluid from each knee joint 10 times: before surgery; 10 minutes, four hours, a day, and three days after surgery; before the second injection; and 10 minutes, four hours, a day, and three days after the second injection.

Analyzing the synovial fluid, the scientists found that lubrication quality decreased gradually over time in the osteoarthritic joints—most notably with a shrinking concentration of hyaluronan. But that decrease was less pronounced, and lubrication quality was better, in the synovial fluid treated with HCSG compared to those treated with saline, Frisbie said. In some cases the fluid had friction-reducing values similar to those found in the synovial fluid taken from the healthy joints.

“We know hyaluronic acid is a normal joint lubricant,” Frisbie said. “It’s made by the joint itself. So it makes sense that just replacing it would be beneficial. Certainly, there’s been a fair bit of research that suggests that this was the case, but this was one of the first times it was investigated at the bioengineering or biomechanical level.”

The affected joints injected with HCSG revealed less wear on the bones and cartilage compared to the saline-injected joints, he said. And while hemorrhaging in the synovial capsule was common in the osteoarthritic joints, it was less frequent and less severe in those treated with HCSG.

As a practicing surgeon as well as a researcher, Frisbie said he is already applying these findings in his clinical experience.

“In cases where I’m doing surgery, and especially when I have questionable joint fluid or it’s clear that there is established osteoarthritis in the joint when we get in there, I often either use that particular product, or hyaluronic acid, at the time of surgery and at the time of suture removal as well, based on this study,” he said.

The study, “Effects of an articular cartilage lubrication with a viscosupplement in vitro and in vivo following osteochondral fractures in horses,” was published in the American Journal of Veterinary Research in August 2021.