Ultrasound probably does not help most knee pain and arthritis

As promised only half an hour ago, here’s some more ultrasound information. This time I’m zooming in on one of SaveYourself.ca’s most important topics: knee pain, especially patellofemoral (kneecap) pain. Does ultrasound help knee pain? No, it probably does not.

As described in detail in my last post, ultrasound is generally understudied, for such a popular therapy, but it is almost completely unstudied with regards to its effectiveness in the treatment patellofemoral pain syndrome. In fact, in 2001, a Cochrane (good!) review of ultrasound therapy for patellofemoral pain syndrome found only one scientific study to report on. And nothing new has been published since then. The almost inevitable conclusion, then:

No conclusions can be drawn concerning the use or non use of ultrasound for treating patellofemoral pain syndrome. More well-designed studies are needed.

Although the authors rightly cautioned that there wasn’t enough evidence to actually draw any conclusions, the scrap of evidence they had to work with did not show a benefit:

Ultrasound therapy was not shown to have a clinically important effect on pain relief for patients with patellofemoral pain syndrome.

It’s hardly surprising: patellofemoral pain syndrome is not one condition. There are many different paths to patellofemoral pain, and thus it is extremely unlikely that any one therapy could possibly have a therapeutic effect on any more than two or three of all the possible causes. On the one hand, it’s certainly possible that some cases of PFPS might respond positively to therapeutic ultrasound. On the other hand, it’s extremely unlikely that many cases would. My opinion is that this puts ultrasound in the “worth a shot” category of therapies, but only just barely.

What about research on ultrasound for osteoarthritis?

Perhaps we can draw some conclusions about the effect of ultrasound on knee osteoarthritis in general? We know that patellofemoral pain syndrome and arthritis are not the same thing, but that they may have some things in common. Thus, if ultrasound were effective for osteoarthritis, perhaps it might be effective for PFPS as well.

But those are big ifs!

Ultrasound for osteoarthritis has been studied a little bit more than ultrasound for PFPS, but the science is still amazingly sparse … and is mostly inconclusive or negative. Another Cochrane review, published in tandem with the one mentioned above, found three times as many scientific tests to report on — for a grand total of three! (Scientific reviews usually find dozens of studies to analyze.) Their findings? The usual:

Ultrasound therapy appears to have no benefit over placebo … for patients with knee osteoarthritis.

And another review — the only other review I know of on this topic, and much more recent — still found nothing to get excited about: the authors came to the familiar conclusion that “the effect of ultrasound is unclear (low-quality evidence).” Remember, although absence of good evidence is not good evidence of absence, if ultrasound actually worked half decently for osteoarthritis of the knee, it should have been fairly obvious even with minimal scientific testing.