Red Light Therapy for Tendon Injury: Scientific Evidence

Patients with long-standing shoulder tendon pain from sports injuries were treated with several methods at once in a 2022 observational study in the United States. The approach combined 658 nm red light and 810 nm near-infrared light at 10 and 50 mW in 25-minute sessions across 35 days with other clinical methods, in patients whose pain had persisted after standard rest, ice, compression, elevation, and anti-inflammatory medicine. Pain eased under the combined approach. However, because several treatments were given together, the contribution of light on its own cannot be separated.

Placebo was not used in a 2022 randomized controlled trial that instead compared 5 active treatments for shoulder tendon pain. 75 patients aged 45 to 70 were split into 5 groups of 15, receiving ultrasound alone, 850 nm near-infrared light alone, 640 nm red light alone, infrared light with ultrasound, or red light with ultrasound, at 40 and 120 mW/cm², delivering 22.5 J across 28 days. Infrared light combined with ultrasound improved significantly on all 12 measures studied, while infrared light, red light, and red light with ultrasound outperformed ultrasound alone on 9, 7, and 10 measures. Shoulder movement rose by an average of 25.8° in the 2 infrared groups, so combining infrared light with ultrasound appeared the strongest of the 5 options.

Whether laser light acts differently at each stage of tendon repair was examined in a 2022 review of laboratory findings. The review covered 600 to 1000 nm light at 3 to 50 J/cm², setting out effects in the inflammatory phase, the rebuilding phase, and the remodeling phase of repair, drawn from cell and animal work rather than patient trials. Light appeared to act through different routes at each stage, promoting new blood vessels early and new tissue later. This review describes possible mechanisms rather than measuring outcomes in patients.

Across 835 participants pooled from randomized controlled trials, a 2021 meta-analysis assessed red and near-infrared photobiomodulation (PBM) as an addition to treatment for tendon conditions. 6 databases were searched through August 2020 for trials comparing PBM against a sham or another treatment, with the pooled trials using 810 to 905 nm light at 0.5 to 5 J/cm² across 14 to 28 days. Benefit appeared for some tendon conditions and some outcomes but not uniformly across the pooled trials. The review noted that high-quality evidence supporting routine use is still lacking despite frequent clinical use.

Applying light over the repaired tendon rather than to the whole hand, a 2018 randomized controlled trial tested low-level laser therapy (LLLT) added to recovery from finger tendon surgery. 97 patients with 114 injured fingers across 3 zones of the hand were divided unequally, with 39 receiving 8 to 10 sessions of red and near-infrared light at 660, 810, and 890 nm over the repaired area across 28 days and 58 forming the control group. Passive movement of the fingers improved earlier in the group given light. Adding light to standard rehabilitation appeared to speed early recovery after this surgery.

Only 3 articles met the criteria in a 2015 review of laser treatment for tendon pain, drawn from 4 databases. The included studies used 810, 820, and 904 nm near-infrared light at 20 to 100 mW/cm², delivering 5.4 and 18 J across schedules ranging from a single session to 56 days. All 3 showed low-level laser therapy to be effective compared with a placebo. The review described the evidence as consistent while calling for more studies on the topic.

According to a 2015 randomized controlled trial in Germany, 2 treatments for long-standing tennis elbow both succeeded when tested against each other. 52 patients were split evenly, with 26 receiving 3 injections of their own conditioned plasma and 26 receiving 12 applications of 830 nm near-infrared light at 7 J/cm², followed by standard physical therapy for everyone, and assessed before treatment, at 2 and 6 months, and at 1 year. 63.5% of all patients were treated successfully, counted as more than 30% improvement in pain and more than 10.2 points on an arm, shoulder, and hand difficulty score. The trial labeled the laser arm as its control group.

41 athletes treated at a single hospital in Japan received low-level laser therapy (LLLT) for sports injuries in a 2013 observational study. The group was 22 men and 19 women averaging 38.9 years of age, with 830 nm near-infrared light applied to painful points or acupuncture points for 10 to 15 seconds per site, up to 10 times per patient and 4.1 times on average. Pain relief scores fell far enough to count as effective in 65.9% of patients, or 27 of the 41 treated. Laser therapy appeared to help across a mix of knee, elbow, heel, groin and shoulder injuries, though no comparison group was used.

Researchers in Iran tested whether adding 830 nm laser to ultrasound and exercise helps inflamed shoulder tendons in a 2012 randomized controlled trial. 42 patients were split evenly, with 21 receiving laser added to ultrasound and exercise and 21 receiving ultrasound and exercise alone, across 10 sessions over 30 days using near-infrared light at 30 mW and 1 J/cm², and outcomes were measured before treatment, at 4 weeks, and again 2 months later. Pain, tenderness, and shoulder function improved significantly in both groups, but muscle strength improved significantly only in the group given laser. Adding laser appeared to contribute something the other treatments did not.

Comparing an exercise program supplemented with low-level laser therapy (LLLT) against the same program supplemented with polarized polychromatic light, a 2009 clinical trial examined tennis elbow. 50 patients with pain on 1 side lasting at least 4 weeks were allocated in sequence to 1 of the 2 groups, all doing lengthening and stretching exercises for the wrist, with the laser group receiving continuous 904 nm near-infrared light at 130 mW/cm² delivering 0.585 J per point and the other group receiving light spanning 480 to 3400 nm at 40 mW/cm² and 2.4 J/cm², across 28 days. The laser group did better than the polychromatic light group on the trial's measures. Adding laser to exercise appeared more useful than adding broad-spectrum light.

Pain during sport eased in 85.7% of weight lifters treated for inflammation where the tendon below the kneecap attaches, in a 1996 clinical trial. 21 knees in 15 competitive athletes received 632.8 nm red light from a helium-neon laser at 5 mW, applied to standard acupuncture points. 81% still reported less pain at 3 months, while local tenderness improved in 57.1%. Laser applied at acupuncture points appeared to ease this knee condition, though without a comparison group the result cannot be attributed to the light alone.

Comparing active laser against a dummy laser and against drug treatment, a 1989 randomized controlled trial examined inflamed shoulder tendons. 30 patients were randomly allocated to 904 nm near-infrared laser 3 times weekly for 2 weeks, to a dummy laser, or to an anti-inflammatory painkiller, with arm movement measured objectively and pain, stiffness, movement, and function rated by the patients at the start and at 2 weeks. Active laser improved significantly over the dummy on all 7 assessments, with shoulder flexion about 15° and lifting the arm sideways about 20° better, and pain 2.5 cm better on a 10 cm scale. The painkiller improved only movement and function against the dummy, so laser appeared the stronger of the 2 active treatments here.

52 people with moderate damage to the tendon supporting the arch of the foot were randomly assigned to laser therapy or to insoles, in a 2021 randomized controlled trial. The laser group received 850 nm near-infrared light at 0.7 to 7 J/cm² in 6-minute sessions across 14 days, with foot pain, function, and the strength of the muscles turning the foot inward and outward measured before treatment, after treatment, and again at 9 months. Both groups improved significantly in foot pain and function straight after treatment, but at 9 months the insole group had the better values. Laser appeared to help in the short term without holding its advantage.

A 2020 review assessed systematic reviews containing only randomized controlled trials to judge which treatments improve pain and function in tendon conditions of any type or location. 5 databases were searched, and the reviews found were scored for methodological quality using a standard tool, with 904 nm near-infrared light among the treatments covered alongside exercise programs and surgery. Effectiveness across the treatments examined remained ambiguous. The review concluded that the evidence does not clearly establish which of these treatments work.

Whether laser therapy relieves the pain of long-standing tendon conditions was the question behind a 2016 critically appraised review. The review examined trials using 770 to 1070 nm light at doses from 5.4 to 400 J/cm², applied in contact with the skin across schedules up to 56 days, in people whose sport was limited by tendon pain and reduced movement and strength. Pain relief appeared at some dose and wavelength combinations but not others. The review concluded that laser can ease tendon pain when the settings are chosen carefully.

This 2015 randomized controlled trial compared low-level laser therapy (LLLT) against ultrasound treatment for an inflamed tendon sheath on the thumb side of the wrist. 30 patients averaging 36 years of age were randomly split between the 2 treatments, each receiving 7 sessions on alternate days across 13 days, with the laser group given 830 nm near-infrared light at 30 to 40 mW and 800 mW/cm², delivering 3 J/cm² in contact with the skin. Tenderness improved in 25 of the 30 patients and pain scores in 25 as well, without a clear advantage for either treatment. The trial found the evidence on comparative effectiveness for this condition remains thin.

81 patients with long-standing tennis elbow were divided between an injection of their own blood components and laser therapy, in a 2014 observational study in India. 39 received the injection, and 42 received 904 nm near-infrared light at 3.5 J/cm² in sessions of 5 to 10 minutes across 10 days, with elbow pain, tenderness, pain on bending the wrist back, grip strength, and swelling assessed repeatedly over at least 52 weeks. Elbow pain scores at final follow-up favored the injection group. Light was the comparison treatment in this study rather than the treatment under test.

A 2012 randomized controlled trial tested whether adding low-power laser to standard physiotherapy helps patients with shoulder pain from rotator cuff problems. 50 patients referred to a rehabilitation clinic were randomly split, with 25 receiving routine physiotherapy alone and 25 receiving that plus 830 nm near-infrared light at 100 mW and 4 J/cm² for 20 seconds per point, and pain, arm movement, and daily function were all measured. Both groups improved, with pain scores falling by 4.16 points in the laser group against 2.68 in the control group, a significant difference, while shoulder movement showed no difference between them. Adding laser to physiotherapy appeared to give a partial rather than a clear benefit here.

Whether the dose and settings used explain the mixed results for laser in tendon pain was examined in a 2010 meta-analysis. 8 databases were searched through August 2008 for controlled trials using low-level laser therapy (LLLT) as the main treatment for any tendon condition, with method quality scored out of 10, and the pooled trials spanning 632.8 to 1064 nm at doses from 1 to 150 J/cm². Results depended heavily on the settings used, with benefit appearing at some doses and not others. The review concluded that dosage and irradiation settings are central to whether LLLT works, and questioned the validity of current dosage recommendations.

25 patients with 41 injured finger tendons across 5 anatomical zones took part in a 2004 clinical trial of laser treatment added to hand rehabilitation. The trial used a placebo-controlled double-blind design, with 21 digits in 13 patients receiving whirlpool treatment and 904 nm near-infrared laser pulsed at 100 Hz from day 8 to day 21 after surgery, and 20 digits in 12 patients receiving the same routine with the laser switched off, alongside a standard rehabilitation program for everyone. Swelling fell significantly more in the laser group, while pain, grip strength and hand function showed no difference between the 2 groups. The trial reported this as the first clinical study of laser treatment on human tendons of this kind.

A double-blind design kept patients and assessors unaware of allocation in a 2025 randomized controlled trial of low-level laser therapy (LLLT) after surgery on the tendons that straighten the fingers. 55 patients, 44 men and 11 women, averaging 34.2 years of age, all followed a controlled movement program, with 1 group receiving 1064 nm near-infrared light at 25 mW/cm² and 7.5 J/cm² for 5 minutes across 10 sessions and the other a sham laser, with assessments at the start and at 4 and 8 weeks. Both groups improved on every measure except wrist movement at week 8, and pain, arm and hand difficulty scores, and hand dexterity showed no difference between them at either week 4 or week 8. The trial found no added benefit from LLLT alongside standard rehabilitation.

19 patients with an inflamed lining around the thumb tendons at the wrist were randomly split between high-intensity laser therapy (HILT) and a sham version in a 2023 randomized controlled trial in Thailand. Both groups wore a thumb splint and did therapeutic exercises, and the laser group received 9 sessions of 1064 nm near-infrared light at 8 and 80 J/cm², delivering 80 and 800 J, 3 times per week across 21 days. Pain, grip strength, and a wrist and hand difficulty score showed no significant differences between the groups. The trial found no additional effect from adding HILT to splinting and exercise.

Across 7 systematic reviews meeting its criteria, a 2018 umbrella review assessed low-level laser therapy (LLLT) for tennis elbow. 5 of the 7 were of moderate methodological quality and 2 of low quality, with the pooled trials spanning 632 to 1064 nm at 0.4 to 4 J/cm², and outcomes covering short- and long-term function, pain, grip strength, and a global rating of improvement. The reviews did not agree with each other, and the quality of the underlying evidence limited what could be concluded. The review found the case for recommending laser in this condition unsettled.

Across 9 randomized controlled trials identified from 6 databases, a 2005 review assessed low-level laser therapy (LLLT) for tennis elbow. Trials were included only if they used LLLT in patients with tennis elbow and reported at least 1 clinically relevant outcome, and their quality was rated using a standard scoring method. The included trials had satisfactory methods but still showed poor results for the effectiveness of LLLT in this condition. The review found the evidence did not support recommending it.

A double-blind design kept both patients and assessors unaware of allocation in a 1993 randomized controlled trial of laser therapy for inflamed shoulder tendons. 35 patients were randomly allocated to an active 830 nm near-infrared laser or a dummy laser, given twice weekly for 56 days in contact with the skin over the shoulder for 10 minutes, delivering 1 and 3 J, with movement range, painful arc, resisted movement, and 4 separate pain and function ratings measured every second week. All responses improved from the starting point, but no difference appeared between the 2 groups on any measure. The trial found no evidence that laser therapy works for this condition.