February 24, 2011 / 5:26 PM / 6 years ago

Shockwave therapy fails in study of 'jumper's knee'

NEW YORK (Reuters Health) - A therapy that uses sound waves to heal injured tissue may not be much help for athletes with "jumper's knee" -- at least when the treatment is used alone, a new study suggests.

The findings, reported in the American Journal of Sports Medicine, add to the conflicting body of research on whether so-called shockwave therapy is effective for tendon problems and other injuries.

Shockwave therapy delivers focused sound waves to areas of injured body tissue, via a hand-held probe placed on the skin.

It has been studied, with mixed results, as an alternative treatment for a range of orthopedic injuries, when more-conservative therapies fail. Those include heel pain caused by a condition called plantar fasciitis, as well as tennis elbow, Achilles tendon injuries, hamstring tendon injuries and "frozen" shoulder.

In the U.S., shockwave devices are approved for treating plantar fasciitis and tennis elbow. The therapy is more widely used in Europe, where it was developed.

For the new study, researchers led by Dr. Johannes Zwerver, of the University Medical Center Groningen in the Netherlands, recruited 127 adult athletes with patellar tendinopathy -- an injury to the tendon that runs from the kneecap to the shinbone.

Patellar tendinopathy is often called "jumper's knee" because it's most common among athletes in sports that involve frequent jumping, such as basketball and volleyball.

Zwerver's team randomly assigned the athletes to one of two groups: One group received three sessions of shockwave therapy over three weeks; those in the placebo group thought they were receiving the therapy, but the sound waves were not actually delivered.

Over the five months following treatment, the study found, athletes in both groups reported improvements in pain and their ability to play their sport. But there was no advantage of shockwave therapy over the placebo.

In an email, Zwerver said that the findings do not mean that shockwave therapy has no value.

The athletes in this study, he explained, were all still active in their sport -- either basketball, volleyball or handball -- and shockwave therapy was the only treatment they were getting.

"We believe that (shockwave therapy) might play a role as a part of a more comprehensive rehabilitation program in which at least the tendon load is reduced -- less training and games for the athletes -- and in which exercise therapy is used to increase strength, coordination and flexibility," Zwerver said.

The severity of the tendon injury may also be important, according to the researchers. In past studies that have found shockwave therapy effective for patellar tendinopathy, patients have had long-standing symptoms and generally failed to improve with other therapies.

In this study, the athletes had had symptoms for less than a year.

Zwerver said that shockwave therapy may be best reserved for chronic, stubborn cases of patellar tendinopathy. In those cases, the tendon may have degenerated more, and animal research, Zwerver noted, suggests that shockwave therapy might aid regeneration of the tissue.

No one is completely sure, however, how shockwave therapy works.

A leading theory is that "microtrauma" to the treated tissue boosts blood flow to the area, promoting natural tissue repair. The therapy is generally safe, but can cause side effects like swelling, pain and skin irritation at the site of the treatment.

In general, shockwave therapy is considered a last resort to avoid surgery when other non-invasive therapies fail. Those include rest, exercise therapy and, for short-term pain relief, anti-inflammatory painkillers and corticosteroid injections.

But all of those options have had limited benefits in treating patellar tendinopathy, according to Zwerver. In general, he said, chronic tendon injuries remain a difficult problem to manage.

So whether people with jumper's knee can find relief with shockwaves is still up in the air. And if you want to try it, you may have to pay for it yourself.

In the Netherlands, Zwerver said, the cost of one shockwave session is about 50 euros ($69 US), and health insurance does not cover it. In the U.S., prices vary, and so does insurance coverage.

The Germany-based company Wolf GmbH provided the shockwave devices used in the current study. None of the researchers reports any financial relationship with the company.

SOURCE: bit.ly/egDCLS American Journal of Sports Medicine, online February 1, 2011.

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