Red Light Therapy for Frozen Shoulder: Scientific Evidence

45 adults aged 18 to 65 with frozen shoulder took part in a 2023 prospective randomized controlled trial comparing high-intensity laser therapy (HILT) combined with stretching exercise against low-level laser therapy (LLLT) combined with stretching exercise. Of the 45 enrolled, 40 completed the study and were split into 2 groups of 20, each treated at the shoulder joint 3 times per week for 3 weeks, with HILT delivered at 1064 nm and LLLT at 904 nm, and outcomes measured using the Visual Analog Scale (VAS) for pain, the Shoulder Pain and Disability Index (SPADI) for function, and a shoulder movement measurement tool. Researchers found that both groups showed significant improvement in pain and function scores after 3 weeks, but the improvement was significantly greater in the HILT group than in the LLLT group. No injuries or musculoskeletal complications were recorded in either group during or after treatment.

Researchers in 2021 tested high-intensity laser therapy (HILT) in a prospective, double-blinded, sham-controlled randomized trial of 36 patients with frozen shoulder, assigning participants to HILT plus therapeutic exercises, sham laser plus therapeutic exercises, or therapeutic exercises alone. All 3 groups received 25 minutes of supervised shoulder exercises per session, with the HILT group treated at 1064 nm and 100 J/cm2 for 15 minutes, 5 times per week over 3 weeks, and pain, disability, quality of life, and shoulder movement were measured at baseline, post-intervention, and at 12 weeks. The study reported that HILT plus exercises produced significantly greater reductions in pain and improvements in quality of life scores compared to both the sham laser and exercise-only groups, while all 3 groups showed comparable gains in shoulder disability and range of motion. 1 patient in the HILT group reported an allergic reaction to laser treatment during the study.

Comparing 3 treatments for frozen shoulder in 84 diabetic patients, a 2012 randomized controlled trial assigned participants to drug therapy plus shoulder exercise alone (control group), linearly polarized near-infrared irradiation (LPNII) added to the control therapy, or LPNII combined with warm air heat therapy added to the control therapy. All 3 groups received daily sessions at 780 to 1400 nm over 20 days, with pain measured by a standard pain rating scale (VAS) and shoulder movement measured by a shoulder movement score. Both LPNII groups were associated with significantly lower pain and shoulder movement scores than the control group after 20 days, and the LPNII plus warm air heat therapy group was reported to have a higher cure rate than either of the other 2 groups.

Across 4 weeks, 8 weeks, and a 16-week follow-up, low-power laser therapy (LLLT) was associated with reductions in pain and disability than placebo in a 2008 randomized controlled trial of 63 patients with frozen shoulder. The active laser group of 31 received treatment at 810 nm and 60 mW across 8 points on the shoulder for 30 seconds each, twice per week for the first 4 weeks and once per week for weeks 5 to 8, totalling 12 sessions, while the placebo group of 32 received sham treatment on the same schedule. Overall, night, and activity pain scores, as well as shoulder pain, disability, and arm function scores were all reported to be significantly lower in the active LLLT group than in the placebo group, while range of motion showed some improvement that did not reach statistical significance.

A narrative review published in 2025 examined the physiological mechanisms and clinical effects of photobiomodulation (PBM) using a 650 nm diode laser for frozen shoulder (adhesive capsulitis). The review searched PubMed, Cochrane, EMBASE, and Web of Science databases covering 2015 to 2024, focusing on protocols using irradiance of 2 to 12 mW/cm2, fluence of 2 to 12 J/cm2, session durations of 5 to 30 minutes, and treatment courses of 3 to 8 weeks applied to the shoulder. A quantitative meta-analysis was not performed due to heterogeneity across study protocols, and findings were instead presented as a narrative synthesis. Across the cited clinical studies, PBM was associated with reductions in pain scores, improved range of motion, and faster functional recovery in patients with frozen shoulder, though the authors noted it may be most effective as part of a multimodal treatment plan.