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Joint lube still useless

 •  • by Paul Ingraham
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Weekly nuggets of pain science news and insight, usually 100-300 words, with the occasional longer post. The blog is the “director’s commentary” on the core content of a library of major articles and books about common painful problems and popular treatments. See the blog archives or updates for the whole site.

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An old-style oil can rendered in shiny metal.

A creaky hinge needs lube. Why not your knee?

It’s common for overzealous orthopaedic surgeons and sports medicine specialists to recommend the injection of artificial “lubricant” into knees and other arthritic joints, or for a “pseudo-arthritis” like patellofemoral syndrome (PFPS). The actual substances are “hyaluronan” and “hylan,” which are basically synthetic replacements for the slippery component of the fluid in your joints (the synovial fluid). “Joint lube,” in other words — which seems like a great idea. Unfortunately, it sounds way better than it is.

Piling on to many years of negative research, a 2022 review was particularly, resoundingly negative:

Strong conclusive evidence indicates that viscosupplementation leads to a small reduction in knee osteoarthritis pain compared with placebo, but the difference is less than the minimal clinically important between group difference. The findings do not support broad use of viscosupplementation for the treatment of knee osteoarthritis.

Geez, science, tell us what you really think. Negative conclusions are rarely this decisive!

This review was huge: they looked only at large, placebo-controlled trials, and they found 24 four of those (which is kind of amazing), with 9000 study subjects. So more research not needed, for once! That’s really a lot of data.

They decided on a clinically significant threshold in advance: “you must be this tall to be considered effective.” Good researchers! Viscosupplementatation was not “tall” enough. It did have small benefits not seen with placebo, but do not be fooled by this positive-sounding detail: it is a formal damned-with-faint-praise conclusion (as opposed to me just pointing it out like usual). The praise is so faint that it is officially not actually praise. Just because the data shows that something was slightly better than placebo doesn’t actually mean that it actually is “slightly better.” What it means is that a bunch of data produced that signal… and the smaller the signal, the more likely it is to be an illusion, artifact. So “slightly better than placebo” really does mean “probably just doesn’t actually work, not even a little bit.”

But if you’re still tempted by that shred of optimism, I’ll leave you with this caveat:

Strong conclusive evidence indicates that viscosupplementation is also associated with an increased risk of serious adverse events compared with placebo.

Play stupid games, win stupid prizes! Serious ones. Obviously it’s not a particularly dangerous procedure, and most people are fine, but the data is clear: the benefit is tiny if it exists at all, while some people really do get seriously hurt.

 See my knee-lube page for more detail … not that you really need more than this.