I’ve been a runner—on and off—for over 25 years. For years, my goal was qualifying for the Boston Marathon. But I was never quite fast enough for my age group. At one point, I figured if I could just hold my best marathon time for another 20 years, I’d eventually “age into” a qualifying time. Unfortunately, my musculoskeletal system has other plans. Every time I increase my training intensity or distance, something breaks down. Usually, it’s Achilles tendinopathy—the bane of every runner’s existence.
Extracorporeal Shockwave Therapy (ESWT) is commonly offered as part of rehabilitation programs. Introduced in the 1980’s it is a non-invasive treatment used for a wide number of musculoskeletal disorders, including plantar fasciitis, Achilles tendinopathy, and rotator cuff disease. Through the delivery of acoustic waves to targeted tissues, ESWT is thought to to stimulate and accelerate healing and reduce pain. Despite widespread use, the efficacy of ESWT is not clear, with mixed results in clinical trials Given I’m currently limping and cursing my Achilles, I felt it was a good time to review the evidence and controversy associated with ESWT, so I’ll be better prepared when it’s offered to me at my next physiotherapy appointment.
What is ESWT?
ESWT delivers pressure waves (“shock waves”) using a handheld device applied to the skin. Compared to the more common ultrasound, ESWT is lower frequency, but higher energy. Shock wave therapy is used to (effectively) treat kidney stones, and it’s changed that surgical procedure into a treatment that doesn’t require an incision. The idea with ESWT seems to be that it stimulates healing by creating controlled microtrauma: promoting increased blood flow and cellular repair. The therapy has also been proposed to “reset” pain signaling pathways, leading to a decrease in perceived pain. It has also been suggested ESWT can disrupt chronic inflammation, encourage tissue repair, and even break down calcific deposits, particularly in tendons and fascia. However, the mechanism of action – if there is one – is not well defined, nor has it been proven.
How ESWT is used
ESWT is commonly used to treat musculoskeletal injuries. These include plantar fasciitis, Achilles tendinopathy, patellar tendinopathy, lateral epicondylitis (tennis elbow), calcific tendinitis of the shoulder, and even stress fractures. Treatment protocols vary depending on the condition, but generally involve a series of sessions over weeks during which focused or radial shockwaves are applied to the affected area. Energy levels or “doses” start low and are increased as tolerated. The non-invasive nature of ESWT, coupled with its relatively low risk profile, has made it an appealing option for both clinicians and patients seeking alternatives to surgery.
Evidence For and Against ESWT
Given ESWT is so widely available from health care professionals, it would be reasonable to assume that there is a good evidence base for the therapy – but that is not the case. While there are some positive trials, there are also negative trials and the overall body of evidence is surprisingly poor.
A 2008 trial found that radial ESWT significantly improved pain and function in a randomized controlled trial in 245 patients with chronic plantar fasciitis compared to placebo. The UK National Institute for Health and Care Excellence (NICE) has cautiously endorsed ESWT for plantar fasciitis and Achilles tendinopathy, stating that while evidence is limited, it supports its use under certain protocols. Additionally, some evidence supports its use in non-union fractures and patellar tendinopathy, though these indications are less well studied.
Despite some promising results, the overall evidence base for ESWT is inconsistent and often methodologically weak:
The Cochrane Collaboration looked at ESWT for rotator cuff disease and concluded that, with moderate certainty, it does not improve pain and function compared with placebo. The review noted small sample sizes, a variety of treatment protocols, inconsistent outcome measures, and short follow-up durations.
A 2024 scoping review of ESWT evaluated methodological and reporting qualities of published systematic reviews on tendinopatihes. It included 18 systematic reviews and noted the overall methodological quality was “critically low”, with only 16% of studies having a low risk of bias.
A 2024 systematic review and meta-analysis examined the effects of ESWT on rotator cuff tendinopathy. It include 16 randomized controlled trials with over 1000 patients. It concluded ESWT significantly improved pain and function compared to control groups. However, the authors noted that the evidence is currently limited and “further research and clinical trials may be required”.
A 2024 critical overview analyzed eight systematic reviews and meta-analyses on ESWT for knee osteoarthritis. It concluded the methodological quality of these reviews was generally unsatisfactory, with only 3 out of 49 outcome indicators assessed as moderate quality, with the rest rated at low or very low quality, suggesting that the reliability of the results of systematic review and meta-analyses is compromised by the poor quality of the included studies.
Friend-of-the-Blog Paul Ingraham has an extensive article on ESWT, reviewing far more articles. He noted “bizarre lack of quality research”, which does not substantiate the hype about this therapy. Moreover, the mechanisms of action remain poorly understood, and there’s ongoing debate over whether the observed benefits are due to the shockwaves themselves or placebo and contextual effects (I’m looking at you, acupuncture).
Side Effects
ESWT seems to be generally well tolerated, but it can cause pain at the application site as well as bruising, skin blistering, edema, and skin and nerve irritation. Exacerbation of symptoms has been reported. More serious adverse events are rare, through there are case reports of Achilles rupture following tendinopathy treatment. There is general advice to avoid anti-inflammatory drugs after treatment – not because there is any evidence against this but NSAIDs are thought to have a negative impact on tissue healing. ESWT is not recommended in a number of clinical conditions (e.g., patients with clotting disorders, pregnancy) or in certain locations (e.g., over growth plates in children, around gas-filled tissues). The poor research quality may mean that short- and longer-terms harms have not been described.
Pseudo-Quackery?
ESWT is big business in rehabilitative and sports medicine. It’s expensive and potentially painful, but the benefits have not been clearly established. While there is published evidence to support some uses, the broader evidence base has significant methodological limits, conflicting results, and a lack of high-quality, long-term studies. How ESWT works remains unclear. Its benefits maybe driven more by placebo, hype and hope than by a true physiological effect. Until there is better evidence, clinicians and patients alike should look at ESWT cautiously. As for me, I’m not planning on ESWT for my Achilles pain. Boston will have to wait – as long as I’m still running in my sixties, I may have a chance.