SAN FRANCISCO — Because there are at least six commercial products available for viscosupplementation with hyaluronic acid, it can be hard to determine which to use, according to Dr. Anthony Luke, who provided tips and clinical pearls at a conference on sports medicine sponsored by the University of California, San Francisco.
Viscosupplementation with hyaluronic acid derivatives is FDA approved for treatment for mild knee osteoarthritis. However, available hyaluronic acid products differ in molecular weight, concentration, and suggested dosing, said Dr. Luke of the university.
The molecular weight of hyaluronic acid in synovial fluid is 6,000–7,000 kd, so one would expect that products at 6,000 kd, the closest in molecular weight to the natural substance, might perform best, Dr. Luke said. However, one study suggests that high-molecular weight injections result in better pain relief than low-molecular weight injections (Clin. Ther. 1999;21:1549–62), and another determined that the effect of hyaluronic acid on osteoblasts increased with molecular weight (Bone 2003;33:703–10).
On the other hand, low-molecular weight preparations may achieve higher concentrations in the desired tissue, he said. A recently published randomized controlled trial demonstrated that two hyaluronic acid preparations of different molecular weights were both more effective than placebo, but there was no statistically significant difference between them (Rheumatol. Int. 2006;26:325–30).
Studies have shown that viscosupplementation is similar to steroid injections in success in reducing pain in mild osteoarthritis, he said. But viscosupplementation appears to have a more prolonged effect than corticosteroids.
Dr. Luke said that he prefers a superolateral approach with a 1.5-inch needle, finding it to be more accurate than the bent-knee approach. If the patient's knee has an effusion, it should first be drained with a 22-gauge needle to avoid diluting the hyaluronic acid.
Dr. Luke said that he occasionally uses the treatment in patients with severe osteoarthritis of the knee who can't take steroids.