Red Light Therapy for Shoulder Impingement: Scientific Evidence

In 2015, a systematic review and meta-analysis pooled 17 randomized controlled trials to evaluate low-level laser therapy (LLLT) for shoulder tendinopathy, making it the first review focused solely on this condition. The included trials used wavelengths of 632 to 1064 nm applied to the shoulder tendons and were grouped by whether LLLT was used alone, alongside exercise, or as part of a broader physiotherapy program, with pain relief on a 100-point scale and overall improvement rate as the primary outcomes. The review found clinically meaningful pain reductions over placebo for LLLT used alone (20.41 mm) and as an addition to exercise (16.00 mm), with trials using inadequate laser doses reported as ineffective across all outcomes, suggesting that correct dosing may be critical to achieving benefit.

Comparing low-level laser therapy (LLLT), steroid injection, and sham laser in 135 patients with shoulder impingement syndrome, this 2014 clinical trial assigned 45 patients to each treatment group and assessed outcomes at baseline, after treatment, and at 3 and 6 months. The laser group received 904 nm LLLT at 2 J/cm2 for 2.5 minutes, 3 times per week over 9 sessions, while the injection group received 2 steroid injections administered 10 days apart. Both active treatments outperformed sham laser on pain and shoulder function at every follow-up point, and the study found no meaningful difference in outcomes between LLLT and steroid injection.

When low-level laser therapy (LLLT), ultrasound therapy, and home-based exercise alone were compared in a 2023 randomized controlled trial, 60 patients with shoulder impingement syndrome were randomly assigned across 3 groups. The 60 participants, 19 male and 41 female, with a mean age of 51.3 years, each received cold pack therapy and a home-based exercise program, with the LLLT group additionally receiving 850 nm laser at 3 J/cm2 across the shoulder and upper arm sites 5 days a week for 15 sessions, and pain and disability were assessed at baseline, 1 month, and 3 months. At the end, it was found that LLLT plus exercise outperformed exercise alone on activity pain and shoulder disability scores at 1 month, but there were no significant differences among the 3 groups at 3 months, suggesting that the benefit of LLLT may be limited to the short term.

A 2016 systematic review examined multiple electrical and light-based treatments for rotator cuff disease, drawing on 47 randomized controlled trials across 2388 participants to assess benefits and harms. For low-level laser therapy (LLLT) specifically, 2 placebo-controlled trials found results favoring LLLT at up to 3 weeks, though the evidence was rated low quality, and combining LLLT with other physical therapy produced few additional benefits across 10 further trials. The review concluded that LLLT may offer short-term benefit over placebo for rotator cuff disease, but the uncertainty of the evidence means the findings should be interpreted with caution.

Patients with shoulder impingement syndrome took part in a 2019 clinical trial testing whether high-intensity laser therapy (HILT) added any benefit beyond exercise therapy alone. The 46 participants were alternately allocated to either HILT plus exercise or sham laser plus exercise, receiving 15 sessions over 3 weeks at 5 sessions per week, with 1064 nm laser applied at the shoulder joint area at doses of 50 and 250 J/cm2. Of those, 21 patients in the HILT group (mean age 56.7 years) and 22 in the sham group (mean age 61.3 years) completed the full study, with pain and shoulder function assessed at baseline, after treatment, and at 1 and 3 months. No significant between-group differences were found at any time point, suggesting HILT may not add meaningful benefit over exercise alone for this condition.

Researchers in 2010 tested gallium arsenide aluminum low-level laser therapy (LLLT) against placebo laser in 52 patients with shoulder impingement syndrome, with all participants also receiving cold pack application and a structured exercise program 5 days a week over 14 sessions. The laser group (30 patients) received 850 nm LLLT at 5 J/cm2 for 60 seconds across up to 6 painful points, while the placebo group (22 patients) received sham treatment, with the 52 participants having a mean age of 53.6 years and including 33 female and 19 male patients. It was reported that both groups improved significantly in pain, shoulder movement, and disability scores after treatment, but found no significant between-group differences, leading researchers to conclude that LLLT may offer no superiority over placebo for this condition.

44 newly diagnosed patients with shoulder impingement syndrome took part in a 2009 randomized controlled trial comparing gallium-arsenide low-level laser therapy (LLLT) combined with exercise against exercise alone. 22 patients received Ga-As LLLT at 780 to 830 nm across 5 shoulder sites, including the shoulder joint area alongside a 12-week home exercise program, while the remaining 22 followed the same exercise program without laser, with night pain, shoulder pain and disability index, and a shoulder function score measured at weeks 2 and 12. Both groups improved significantly over the study period, but the researchers found no meaningful difference between groups on any outcome, suggesting a home exercise program alone may be equally effective for this condition.

Both the active laser group and the placebo group improved similarly in a 2009 randomized controlled trial of low-level laser therapy (LLLT) for shoulder impingement syndrome. The 67 participants were split into an active LLLT group (34 patients) receiving 630 to 904 nm laser at the shoulder joint area and front of the shoulder, and a placebo laser group (26 patients), with both groups also completing a supervised progressive exercise program and superficial cold therapy 5 days a week for 3 weeks. No significant differences between groups on pain, function, or disability after treatment were found, suggesting LLLT may not provide additional benefit when combined with an exercise program for this condition.