FORBES.COM
MAY 18, 2015
As spring turns into summer, we spend more time outdoors, exercising, gardening, or just walking around. And for many people, more exercise means knee pain. Count me among the afflicted.
Several people, including my orthopedic specialist, have suggested that I try injections of hyaluronic acid to treat my knee pain. Many people swear by it, and even though I looked into this two years ago (and rejected it as ineffective), I thought I would look again. Perhaps the evidence had changed.
It hadn’t.
Superficially, these injections sound reasonable. Hyaluronic acid is already inside your knee and helps to lubricate and cushion the joint. Adding more lubricant seems like a good idea; after all, it works for cars, bicycles, door hinges, or any other creaky joint.
But not for knees. Just recently, Anne Rutjes, Peter Jüni and their colleagues published a very large review of the evidence on knee injections. They looked at 89 trials involving over 12,000 adults and found that in the trials that were properly controlled (blinded), hyaluronic acid injections had either no effect or a “clinically irrelevant effect”; that is, too small a difference to matter to the patient. (They also found five unpublished trials that showed no effect at all; this is a good example of the so-called “file drawer effect”, where studies that don’t have the desired outcome are stashed away in a drawer and never published.)
Rutjes and colleagues also pointed out that there’s a real risk of harm when you inject something deep into the knee joint. To quote their summary for patients (published along with the article):
Viscosupplementation [injection of hyaluronic acid] may provide little if no pain relief or function improvement in patients with knee osteoarthritis. It also seems to increase the risk for adverse events.
If you don’t believe Rutjes, perhaps you’ll believe the American Academy of Orthopaedic Surgeons (AAOS), who reviewed a large body of evidence and wrote:
We cannot recommend using hyaluronic acid for patients with symptomatic osteoarthritis of the knee. Strength of recommendation: Strong.
After looked a numerous studies, the AAOS concluded that there was no clinically meaningful benefit from these injections. This document is their official recommendation for physicians.
I was disturbed, though, to find that the AAOS information for patients directly contradicts their own recommendations to clinicians, and suggests that knee injections might work. On their patient-oriented web page, they offer the wishy-washy comment that “hyaluronic acid does seem to have anti-inflammatory and pain-relieving properties … [that] may last for several months,” though “not all patients will have relief of pain.”