Abstract: Thirty-two trials (2281 participants) met our inclusion criteria. Most trials (25) included participants with rotator cuff disease and calcific deposits, five trials included participants with rotator cuff disease and no calcific deposits, and two trials included a mixed population of participants with and without calcific deposits. Twelve trials compared shock wave therapy to placebo, 11 trials compared high-dose shock wave therapy (0.2 mJ/mm² to 0.4 mJ/mm² and above) to low-dose shock wave therapy. Single trials compared shock wave therapy to ultrasound-guided glucocorticoid needling, ultrasound-guided hyaluronic acid injection, transcutaneous electric nerve stimulation (TENS), no treatment or exercise; dual session shock wave therapy to single session therapy; and different delivery methods of shock wave therapy. Our main comparison was shock wave therapy versus placebo and results are reported for the 3 month follow up. All trials were susceptible to bias; including selection (74%), performance (62%), detection (62%), and selective reporting (45%) biases. No trial measured participant-reported pain relief of 30%. However, in one trial (74 participants), at 3 months follow up, 14/34 participants reported pain relief of 50% or greater with shock wave therapy compared with 15/40 with placebo (risk ratio (RR) 1.10, 95% confidence interval (CI) 0.62 to 1.94); low-quality evidence (downgraded for bias and imprecision). Mean pain (0 to 10 scale, higher scores indicate more pain) was 3.02 points in the placebo group and 0.78 points better (0.17 better to 1.4 better; clinically important change was 1.5 points) with shock wave therapy (9 trials, 608 participants), moderate-quality evidence (downgraded for bias). Mean function (scale 0 to 100, higher scores indicate better function) was 66 points with placebo and 7.9 points better (1.6 better to 14 better, clinically important difference 10 points) with shock wave therapy (9 trials, 612 participants), moderate-quality evidence (downgraded for bias). Participant-reported success was reported by 58/150 people in shock wave therapy group compared with 35/137 people in placebo group (RR 1.59, 95% CI 0.87 to 2.91; 6 trials, 287 participants), low-quality evidence (downgraded for bias and imprecision). None of the trials measured quality of life. Withdrawal rate or adverse event rates may not differ between extracorporeal shock wave therapy and placebo, but we are uncertain due to the small number of events. There were 11/34 withdrawals in the extracorporeal shock wave therapy group compared with 13/40 withdrawals in the placebo group (RR 0.75, 95% CI 0.43 to 1.31; 7 trials, 581 participants) low-quality evidence (downgraded for bias and imprecision); and 41/156 adverse events with extracorporeal shock wave therapy compared with 10/139 adverse events in the placebo group (RR 3.61, 95% CI 2.00 to 6.52; 5 trials, 295 participants) low-quality evidence (downgraded for bias and imprecision). Subgroup analyses indicated that there were no between-group differences in pain and function outcomes in participants who did or did not have calcific deposits in the rotator cuff. Based upon the currently available low- to moderate-certainty evidence, there were very few clinically important benefits of shock wave therapy, and uncertainty regarding its safety. Wide clinical diversity and varying treatment protocols means that we do not know whether or not some trials tested subtherapeutic doses, possibly underestimating any potential benefits. Further trials of extracorporeal shock wave therapy for rotator cuff disease should be based upon a strong rationale and consideration of whether or not they would alter the conclusions of this review. A standard dose and treatment protocol should be decided upon before further research is conducted. Development of a core set of outcomes for trials of rotator cuff disease and other shoulder disorders would also facilitate our ability to synthesise the evidence.

Plain-language summary: We included 32 trials (2281 participants), published up to November 2019. Twelve trials compared shock wave therapy to placebo. Eleven trials compared high- and low-dose shock wave therapy, although dosages varied across trials. Single trials compared shock wave therapy to other treatments including ultrasound-guided glucocorticoid needling, transcutaneous electric nerve stimulation (TENS), exercise, or no treatment; or different regimens of shock wave therapy. Overall, 61% of participants were women, the average age was 52 years, and the average duration of the condition was 33 months. Two trials were funded by manufacturers of shock wave machines. Participant-reported pain relief of 50% or greater (one trial): • four more people out of 100 reported pain relief of 50% or more (ranging from 19 fewer to 26 more). 42 out of 100 people reported pain relief of 50% or greater with shock wave therapy compared with 38 out of 100 with placebo. Pain (higher scores mean more pain) (nine trials): • Improved pain by 8% (ranging from 2% better to 14% better) or 0.78 points better (ranging from 0.17 better to 1.4 better) on a 0- to 10-point scale. People who had shock wave therapy rated their pain as 2.2 points and people who had placebo rated their pain as 3 points. Function (ability to use the shoulder; higher scores meanbetter function) (nine trials): • Improved by 8% (ranging from 1.6% to 14%) or 8 points better (ranging from 1.6 better to 14 better) on a 0- to 100-point scale. People who had shock wave therapy rated their function as 74 points and people who had placebo rated their function as 66 points. Participant-reported success (six trials): • 15% (ranging from 3% fewer to 49% more) more people reported their treatment a success. 41 out of 100 people reported treatment success with shock wave therapy and 26 out of 100 people reported treatment success with placebo. Withdrawals due to side effects (seven trials): • 3% fewer (ranging from 6% fewer to 3% more) people withdrew from treatment due to side effects. 8 out of 100 people withdrew from treatment with shock wave therapy and 10 out of 100 people withdrew from the placebo group. Side effects (five trials): • 19% more people reported side effects (ranging from 7% more to 40% more): 26 out of 100 people had a side effect with shock wave therapy and seven out of 100 people had a side effect with placebo. In people with rotator cuff disease, moderate-certainty evidence (downgraded due to bias) shows that shock wave therapy probably does not improve pain and function compared with placebo, and low-certainty evidence (downgraded due to bias and lack of accuracy) shows there may be no improvement in those with a pain reduction of 50% or more and participant-reported success. We are uncertain if withdrawals or side effects differed between groups due to small number of events. It did not appear to matter if participants had calcific deposits or not. We are uncertain if higher doses of shock wave therapy have benefits with more side effects compared with lower doses, as there was only low- or very low-certainty evidence available, and we cannot recommend a particular treatment dose. Side effects included treatment-related pain, bruising and bleeding although these were generally minor and short-lived. Rare and serious side effects, including loss of blood supply and bone death, while possible, were not reported.