Red Light Therapy for Shoulder Pain: Scientific Evidence

Researchers in Italy published a randomized clinical trial in 2009 comparing high-intensity laser therapy (HILT) with ultrasound therapy for shoulder impingement, a painful condition caused by the trapping of soft tissue beneath the shoulder bone. The 70 participants (42 women and 28 men, mean age 54.1 years) were randomly assigned to either HILT at 1064 nm or ultrasound therapy, with both groups completing 10 sessions over 14 days. Pain, shoulder function, and muscle strength were measured using 3 validated scales before and after treatment. Researchers found that the HILT group showed significantly greater reductions in pain and greater improvements in shoulder movement, function, and strength compared to the ultrasound group, and the pain score difference between groups exceeded the threshold considered clinically meaningful.

A systematic review and meta-analysis published in 2024 examined which combined physiotherapy treatments offered the most benefit over exercise alone for shoulder pain, drawing on 20 randomized trials covering 2,385 participants across treatment programs of 8 to 12 weeks. Among all the combinations tested, adding laser therapy to exercise produced the greatest reductions in shoulder pain and disability scores, with low-level laser therapy showing a larger effect than high-intensity laser therapy, while manual therapy added only limited benefit beyond exercise alone. Despite laser therapy showing the strongest added benefit among all combinations tested, the review stopped short of a firm recommendation and called for more rigorous trials before drawing definitive conclusions.

Comparing low-level laser therapy (LLLT) against placebo and ultrasound for shoulder pain was among the central questions of a systematic review published in 2015 that evaluated multiple passive physical treatments for shoulder pain and related conditions. Researchers screened 1,760 articles and identified 11 trials with a low risk of bias, using wavelengths of 890 nm and 1064 nm applied to the shoulder and surrounding muscles for 2 minutes per point across varying session schedules. The review reported that LLLT provided short-term pain reduction for shoulder impingement, and was found to be more effective than both placebo and ultrasound for this condition. Other passive treatments, including ultrasound, tape, and electrical current therapy, were found to offer no meaningful benefit for the same condition.

Whether low-level laser therapy (LLLT) added to exercise stands against exercise alone for shoulder pain was the central question of a review published in 2013. The review identified 4 randomized controlled trials covering 214 participants in total, with wavelengths ranging from 635 nm to 904 nm applied to the shoulder across treatment programs of up to 21 days, and assessed outcomes of pain and shoulder function. Of the 4 included trials, 2 found significantly greater improvement with LLLT added to exercise, while the other 2 found no significant difference compared to placebo laser plus exercise. The available evidence was too conflicting for the review to draw a clear conclusion in favor of LLLT over exercise alone.

A randomized controlled trial published in 2005 evaluated the effect of low-power gallium-arsenide laser therapy on shoulder pain, specifically involving inflammation of the tendons around the shoulder joint. The 40 participants were split into 2 groups of 20, with one group receiving laser applied at 904 nm to several points across the shoulder joint for 60 seconds per point, combined with an exercise program for 10 sessions over 14 days, while the second group received placebo laser plus the same exercises. The study reported that the laser group showed significantly better tenderness on touch (85% of patients improved vs 30% in the placebo group) and greater shoulder extension, but no significant difference in overall pain, active range of motion, or pressure pain sensitivity compared to the placebo group.