Red Light Therapy for Carpal Tunnel Syndrome: Scientific Evidence

Researchers at a university in Mersin, Türkiye, randomly assigned 42 people with mild to moderate carpal tunnel syndrome, 35 women and 7 men averaging 50 years of age, in a 2022 randomized controlled trial. 22 received 670 nm light at 10 mW, delivering 60 J over the wrist across 15 sessions over 21 days, and 20 received a sham device, with both groups wearing a neutral wrist orthosis. Night-time tingling improved in both groups, while pain, a clinical sign of nerve irritation, symptom severity, and function improved in the treated group alone. The cross-sectional size of the nerve, its flattening, and its blood supply on ultrasound all improved significantly in the treated group only.

Comparing low-level laser against a corticosteroid injection, a 2022 randomized controlled trial treated 87 people with moderate carpal tunnel syndrome at a training hospital in Antalya, Turkey. 44 patients, covering 74 wrists, received 40 mg of a steroid solution into the wrist, while 43 patients, covering 70 wrists, received 830 nm light at 6 J/cm² for 1 minute per point, 5 times a week across 15 sessions over 21 days, and 80 patients completed the 6-month follow-up. Pain and arm disability scores were better in the steroid group at 1 month, but no significant difference remained between the groups at 6 months. Signs of nerve irritation, grip strength, and motor nerve timing improved to a similar degree in both groups, while sensory nerve timing and speed improved only in the steroid group.

60 people with carpal tunnel syndrome were divided into 2 groups in a 2021 randomized controlled trial. 1 group received 15 sessions of elastic taping, and the other received 15 sessions of 830 nm light at 30 mW and 1.5 J/cm² for 5 minutes per session, both over 21 days. Grip strength, pain, nerve pain scores, and questionnaire scores improved significantly in both groups after treatment. Every one of those measures was significantly better in the laser group, as were the timing of the motor nerve signal and the speed of the sensory nerve.

4 of the 5 groups in a 2020 double-blind randomized controlled trial in Iran received either low-level laser or high-intensity laser at a high or a low dose, drawn from 98 people with carpal tunnel syndrome aged 20 to 60. All 5 groups performed the same 4 standard exercises, and the laser groups received 808 and 860 nm light at 50 mW to 1.6 W and 8 or 20 J/cm² for 32 seconds, 76 seconds, 100 seconds, and 4.17 minutes per session, across 5 sessions over 14 days. Pain fell significantly in all 5 groups after 3 weeks, and the timing of the motor nerve signal shortened in all of them. The differences between groups over time were significant for pain, nerve signal timing, and signal size, with high-intensity laser at 1.6 W and the lower dose of 8 J/cm² coming out ahead.

A scanning technique that measures tissue stiffness tracked 37 wrists from 34 people with mild or moderate carpal tunnel syndrome, 27 women and 7 men, in a 2019 observational study. 19 wrists received 670 nm low-level laser light at 100 mW, delivering 4 J alongside a splint, 5 times a week across 21 days, while 18 wrists were treated with the splint alone. Stiffness, the cross-sectional size of the nerve, symptom severity, and function all fell significantly in the group given light. None of those measures changed significantly in the group wearing the splint alone.

Whether laser or ultrasound serves carpal tunnel syndrome (CTS) better was tested in 70 people with mild to moderate disease in a 2019 clinical trial in Poland. 1 group received ultrasound, and the other received 830 nm low-level laser light at 100 mW and 9 J/cm² for 10 minutes per session, 5 times a week across 14 days, with both groups also performing nerve and tendon gliding exercises 3 times a day. Sensory symptoms, pain, grip strength, and questionnaire scores all improved significantly across the whole group after treatment. No meaningful difference appeared between the 2 treatments on any measure, and no adverse effects were observed.

Whether laser acupuncture outperforms a switched-off device was tested in 84 people with mild to moderate carpal tunnel syndrome at a teaching hospital in Taichung, Taiwan, in a 2019 randomized controlled trial. 43 received 810 nm light at 400 mW and 24 J/cm² for 60 seconds at traditional Chinese acupuncture points on the affected side, once a day, 5 times a week across 28 days, while 41 received the same procedure with the device off. Overall symptom scores fell significantly further in the treated group at both 2 weeks and 4 weeks. Nerve conduction measurements showed no significant difference between the 2 groups.

Laser alone, laser with elastic taping, and a sham device were the 3 arms of a 2018 randomized controlled trial covering 64 hands from 37 patients with mild or moderate carpal tunnel syndrome. 21 hands received 685 nm light at 27 mW, 5 J/cm², 10 J, and 10 Hz for about 8 minutes per session, while 22 received the same light plus elastic taping, and 21 received a sham device, all treated 5 times a week across 21 days. Pain and questionnaire scores improved significantly more with laser than with sham at both 3 weeks and 12 weeks, alongside pinch and grip strength at 3 weeks. The group given laser and taping together held significant gains in pain, function, pinch, and grip at both time points.

Researchers in 2017 divided 50 patients aged 25 to 55, all with nerve damage from diabetes and carpal tunnel syndrome on one side, into 2 equal groups in a randomized controlled trial in Egypt. 25 received 904 nm light at 20 mW delivering 4.8 J through a 7 mm probe, applied over both the wrist ligament and the course of the nerve in the forearm, while 25 received ultrasound at 1 MHz and 1 W/cm², for 6 and 15 minutes per session across 18 sessions over 42 days. Both groups treated the ligament and the forearm at the same time. No statistically significant difference emerged between the 2 treatments.

Researchers in Poland randomly assigned 160 people with carpal tunnel syndrome (CTS) to 2 treatment programs in a 2016 randomized controlled trial. 1 group received manual therapy and nerve mobilization techniques, while the other received red and infrared light at 658 and 808 nm alongside ultrasound applied in contact over the wrist ligament, both across 20 sessions given twice weekly over 70 days. The ability to tell 2 nearby touches apart improved significantly in the affected hands of both groups. No statistically significant difference emerged between the 2 programs.

Among 79 people whose carpal tunnel syndrome (CTS) had lasted under a year, a 2014 randomized controlled trial at a rehabilitation institute in Belgrade, Serbia, tested laser against a sham device. 40 received 780 nm light at 30 mW and 38.2 mW/cm² in contact with the skin at 4 points over the wrist for 90 seconds per point, delivering 2.7 J and 3.4 J/cm² per point, while 39 received a sham device, across 20 treatments over 35 days. Pain fell significantly, fewer patients had a positive nerve irritation sign, and both sensory and motor nerve signal timing shortened in the treated group. None of those changes appeared in the placebo group.

2014 brought a double-blind randomized controlled trial in Thailand that assigned 66 people with mild to moderate carpal tunnel syndrome to laser or placebo, with 59 completing across 112 hands. The treated group received 15 sessions of 810 nm low-level laser light across 35 and 105 days, delivering 18 J per session over the wrist at 50 mW alongside a neutral wrist splint, while the placebo group had the splint and a sham device. Grip strength improved significantly more in the laser group at both the 5-week and 12-week follow-ups. The timing of the motor nerve signal was also significantly better in the laser group at 12 weeks.

Comparing laser against transcutaneous electrical nerve stimulation, a 2013 randomized controlled trial treated 20 people with mild to moderate carpal tunnel syndrome (CTS) at a rehabilitation institute. The laser group received a combined 830 and 1064 nm beam at 25 W, delivering 250 J/cm² over the nerve at the wrist for 100 seconds per session, across 15 sessions over 21 and 105 days, while the other group received electrical stimulation at 100 Hz for 30 minutes. Laser improved both the pain and the abnormal sensations, and it was the only one of the 2 to change the nerve conduction measurements. Electrical stimulation produced a clinical improvement in pain that did not reach statistical significance.

29.41% of people given laser after carpal tunnel surgery still had abnormal nerve readings at 6 months, compared with 63.64% of those given a placebo device, in a 2011 randomized controlled trial in Brazil. The trial randomly divided 58 people who had undergone surgery for carpal tunnel syndrome, mostly women and averaging 44.3 years old in the treated group and 51.9 in the placebo group, with 1 group receiving 830 nm light at 30 mW, delivering 3 J, given 10 times over 14 to 70 days after the operation, and the other a placebo device. Fewer patients in the treated group had complaints after surgery than in the placebo group. No adverse effects were recorded.

In 2011, a randomized controlled trial at a medical university in Poland compared low-level laser against pulsed magnetic field therapy in 38 people with carpal tunnel syndrome. 18 received 904 nm light at 75 W, 6 J/cm², 50 J, and 10000 Hz for 5.55 and 15 minutes per session, and 20 received magnetic field therapy, both given in 2 series of 10 sessions separated by a 2-week break. Day and night pain fell significantly in the laser group at every stage of treatment and remained lower 6 months after the last session. In the magnetic field group, that reduction became significant only after the second series.

Published in 2009, this randomized controlled trial divided 100 hands from 50 women with carpal tunnel syndrome on both sides into 3 groups. 1 group wore a splint alone, 1 had a splint plus ultrasound, and 1 had a splint plus 904 nm light at 2.4 mW and 27 W, 1 J/cm², and 1000 Hz, given 5 times a week across 14 days. All 3 groups improved to some degree by the 3-month assessment. Adding either ultrasound or laser to the splint worked better than the splint alone, with laser ahead of ultrasound on symptom severity, pain relief, and patient satisfaction.

Comparing laser against open surgery, a 2007 clinical trial at a national institute divided 60 symptomatic hands from 54 patients equally between the 2. The laser group received 632.8 nm helium-neon light at 12 mW and 3 J/cm², given 12 times over 42 days, while the surgical group had the carpal tunnel released by the standard open approach, with both assessed about 6 months later. Laser produced significant improvement in every symptom the patients reported except muscle weakness, and in every finding on examination except wasting of the thumb muscle. Nerve conduction improved to the same degree after both treatments, and the trial judged laser an effective option for early and mild to moderate cases where pain is the main complaint, reserving surgery for advanced and chronic ones.

Published in 2006, this review from a neurology department at Boston University in the United States examined 7 studies of light therapy for carpal tunnel syndrome covering 293 participants. The 7 studies used wavelengths of 632.8, 660, 670, 780, 800, 820, 830, 860, 870, 880, and 904 nm. 5 of the 7 found a benefit from real laser, 2 of those against a sham comparison, while 2 studies found no advantage over their control condition. The 5 studies reporting benefit had used higher doses at the main treatment sites, ranging from 9 J to 225 J/cm², against 1.8 J or 6 J/cm² in the 2 that did not. Across those 5 studies, the average success rate was 84% over 171 hands, in patients whose pain had lasted about 2 years.

25 people with carpal tunnel syndrome on one side, 22 women and 3 men averaging 47 years of age, took part in a 2005 clinical trial in Leeds, United Kingdom. Polarized polychromatic light spanning 480 to 3400 nm was directed at the wrist from 5 to 10 cm away at 90 W and 2.4 J/cm², for 6 minutes per session, 3 times a week across 28 days. At 4 weeks, 5 patients were free of night pain, 12 were much improved, 6 were slightly improved, and 2 reported no change. At 6 months, 9 were pain-free, 13 improved significantly, and 3 slightly improved.

A 2004 randomized controlled trial in Semnan, Iran, compared ultrasound against low-level laser in 50 patients with mild to moderate carpal tunnel syndrome, covering 90 hands. The laser group received 830 nm light delivering 9 J at 5 points over the wrist, and both groups were treated for 15 minutes per session, 5 times a week across 21 days. Nerve signal timing, signal size, finger pinch strength, and pain all improved significantly more in the ultrasound group than in the laser group. Those differences were still present at the 4-week follow-up.

A crossover design gave each of 11 people with mild to moderate carpal tunnel syndrome (CTS) both a real and a sham series in a 2002 randomized controlled trial at a veterans' medical center in the United States. All 11 had gone 3 to 30 months without responding to standard treatment. Each series ran 3 to 4 weeks in a randomized order, using a 632.8 nm red beam at 15 mW on shallow points of the affected hand, a pulsed 904 nm beam at 9.4 W on deeper points of the arm and neck, and a very low-current nerve stimulator at the wrist, for 35 to 45 minutes per session. Neither device produced any sensation, and the hand was treated behind a curtain so patients could not tell whether it was switched on. Pain scores, sensory nerve timing, and 2 clinical signs of nerve irritation improved significantly after the real series and not after the sham series.

Among 31 people, 22 women and 9 men aged 24 to 84, whose carpal tunnel syndrome had already failed standard medical or surgical treatment, a 1999 clinical trial at an acupuncture practice in Westport, Massachusetts, United States, tested a red beam laser applied at acupuncture points. 36 hands were treated, 14 of them having already failed 1 or 2 surgical release operations, using a 670 nm red beam at 5 mW, delivering 1 to 7 J per point, together with a very low-current nerve stimulator, 3 times a week for 4 to 5 weeks. Pain fell significantly across the group, with 33 of the 36 hands either pain-free or improved by more than half. All 14 hands that had failed surgery were among those successfully treated.

A 2023 randomized controlled trial at a medical school in Konya, Turkey, randomly divided 60 people diagnosed with carpal tunnel syndrome into 2 groups of 30. Both groups wore a splint and did exercises, with 1 group also receiving 1064 nm light in pulsed mode at 8 W and 8 J/cm², followed by continuous mode at 3 W and 80 J/cm², for 84 seconds and 11 minutes per session across 10 sessions over 14 days, while the other received a sham laser. Pain and questionnaire scores improved significantly within both groups over time, with no significant difference between the groups at any point. Grip strength improved significantly more in the laser group in the early period, and the cross-sectional size of the nerve at the wrist narrowed in both groups, though that laser advantage did not hold at the longer follow-up.

Across 3 equally sized treatment groups, a 2020 randomized controlled trial at a university hospital enrolled 42 participants with carpal tunnel syndrome, 31 of them women. 1 group received a steroid injection into the wrist under ultrasound guidance, 1 received 880 nm light at 20 J/cm² for 10 seconds per session across 10 sessions over 28 days, and 1 received an anti-inflammatory gel driven in by ultrasound 3 times a week. All 3 treatments improved pain, symptom severity, and function within their own groups. At 4 weeks, the steroid injection produced the greatest reduction in pain, and the laser produced the greatest improvement in sensory nerve timing. The questionnaire scores and motor nerve timing showed no significant difference between the 3 groups.

Searching 5 research databases up to April 2016, a 2018 review from a rehabilitation department in the Netherlands assessed low-level laser therapy for carpal tunnel syndrome (CTS). It drew on 2 earlier systematic reviews and 17 randomized controlled trials, covering wavelengths from 780 to 905 nm at 30 mW to 75 W and 1.5 to 59 J/cm². The review found strong evidence that laser outperforms placebo over the very short term, meaning 5 weeks or less. Beyond that point, the advantage in pain, function, and recovery diminished, with the evidence at 7 and 12 weeks described as moderate and conflicting.

Across 473 patients and 631 wrists drawn from 8 randomized controlled trials, a 2017 meta-analysis from a physical therapy faculty in Cairo, Egypt, assessed low-level laser against placebo for mild to moderate carpal tunnel syndrome (CTS). The included trials used wavelengths of 632.8, 660, 780, 830, and 880 nm at 30 to 60 mW and 1.6 to 225 J/cm² for 10 minutes per session, given 3 to 5 times a week over 14 to 90 days. Grip strength favored laser significantly, by an average of 2.19 units. Pain scores, symptom severity, and function scores showed no significant advantage for laser, and 1 nerve signal measure favored placebo.

Published in 2017, this meta-analysis from an orthopedic department in Aberdeen, United Kingdom, assessed low-level laser therapy for carpal tunnel syndrome (CTS) against placebo and against other non-surgical treatments. It searched 4 research databases and clinical trial registries up to December 2016, identifying 22 trials that randomized 1153 participants and used 600 to 1000 nm light at 10 to 500 mW. 9 of those trials, covering 525 participants, compared laser against placebo, with 256 participants assigned to laser. The analysis found no data supporting any clinical effect of laser for this condition, rated the evidence very low quality, and found weak evidence that laser is less effective than ultrasound.

How much of the laser power aimed at the wrist actually enters the tissue was measured in a 2016 observational study from a hospital in China, which tracked the light reflected and scattered back from the skin in 30 cases of carpal tunnel syndrome. Near-infrared laser light between 790 and 830 nm was delivered at up to 500 mW, with the effective power inferred from what came back. The proportion reflected varied from 1.8% to 54% between individuals, falling between 10% and 20% in 36.7% of cases and above 40% in 16.7%. The study concluded that the power actually reaching the tissue should be monitored during treatment rather than assumed.

This 2016 meta-analysis from an orthopedic department at Tianjin Medical University assessed low-level laser for mild to moderate carpal tunnel syndrome. It searched 4 databases from the 1960s to October 2015 following Cochrane methods, and 7 randomized trials met the criteria, covering 270 wrists treated with laser and 261 controls at wavelengths of 785, 810, 830, and 880 nm and 6 J/cm² over 42 days. Grip strength at 12 weeks was significantly stronger in the laser group, by an average of 2.04 units, with pain scores and the size of the sensory nerve signal at 12 weeks also favoring laser. The analysis noted high variation between the included trials.

When a 2015 randomized controlled trial in Italy set a manual technique against low-level laser, it enrolled 42 people with carpal tunnel syndrome across 70 symptomatic hands. The laser group received light between 780 and 1400 nm at 3 W in 5 daily sessions lasting 10 minutes each. Both groups improved on a standard symptom and function questionnaire by the end of treatment. The manual therapy group also showed a significant fall in pain and held its gains at 3 months, while the laser group's improvement was not sustained that far.

A 2008 randomized controlled trial in Taiwan randomly divided 36 patients with mild to moderate carpal tunnel syndrome (CTS) between laser and a sham device. 830 nm light at 60 mW, 9.7 J/cm², and 10 Hz was placed directly above the wrist ligament for 10 minutes a day, 5 days a week across 14 days, with the second group receiving a sham device. Pain scores were significantly lower in the laser group than in the placebo group both immediately after treatment and at the 2-week follow-up. Grip strength, symptom scores, and function scores showed no significant difference immediately after treatment, but all 3 favored the laser group significantly at the 2-week follow-up.

A placebo-controlled design split 81 people with carpal tunnel syndrome, 70 women and 11 men averaging 49 years of age, between laser and a dummy device in a 2007 randomized controlled trial. 41 received 830 nm light at 450 mW, delivering 7 J over 2 minutes to the wrist, and 40 received a placebo device, with all patients treated 5 times a week across 10 sessions and wearing a wrist splint at night. Pain, pinch grip, and daily function improved significantly in both groups. Hand grip strength improved in the laser group alone, which also gained on sensory and motor nerve timing, while the speed at which the sensory nerve carried signals improved in both groups.

Researchers in Cuba treated 26 women with carpal tunnel syndrome using non-coherent light from gallium arsenide diodes in a 2001 clinical trial. Each received light between 920 and 940 nm over the wrist for 15 minutes a day across 21 days. Every patient reported that pain and numbness in the affected hand had gone by the end of treatment. The measurements of how fast and how strongly the nerve carried signals were unchanged, which the trial read as the light leaving the larger nerve fibers unaffected.

Neither an anti-inflammatory gel nor laser added anything to nerve and tendon gliding exercises, according to a 2024 randomized controlled trial in Türkiye that randomly divided 45 people with moderate carpal tunnel syndrome (CTS) into 3 groups. 1 group received an anti-inflammatory gel delivered by ultrasound alongside nerve and tendon gliding exercises. Another received 830 nm light at 30 mW, 5.4 J/cm², and 1.8 J for 3 minutes per session, 5 times a week across 21 days, alongside the exercises, while the third received the exercises alone. Symptom, function, and pain scores improved in all 3 groups at both 6 and 12 weeks, and the cross-sectional size of the nerve on ultrasound improved in all 3 at 12 weeks.

According to a 2022 review from a neurology department at a medical university in Poland, light therapy is 1 of many non-surgical treatments used for carpal tunnel syndrome. It searched 2 databases, screened 229 articles, and included those that met its criteria, covering light between 600 and 1070 nm given across 35 days alongside acupuncture, shock wave therapy, fluid injection under the skin, elastic taping, steroid injection, splints, platelet injections, manual therapy, and ultrasound. The review set out what is known about how the nerve is damaged and why each treatment is used. It found every treatment reviewed to be safe, with effectiveness differing between them, and called for further trials on newer methods.

Searching 7 research databases from 2000 to March 2015, a 2017 review from a physiotherapy division in South Africa assessed low-level laser against placebo for pain, hand function and grip strength in carpal tunnel syndrome. 9 randomized controlled trials met the criteria, covering 827 participants and scoring an average of 8.2 out of 11 on a standard quality scale. The treatment regimens varied so widely that combining their results statistically was judged inappropriate, so the review described them one by one. It concluded that no strong evidence exists either way, while noting that the trials using 780 to 860 nm at 9 to 11 J/cm² over 14 to 35 days were the ones worth examining further.

48 people with mild and moderate carpal tunnel syndrome (CTS) were randomly assigned in a 2016 randomized controlled trial in Brazil, with 30 completing the protocol, 90% of them women. Both groups wore a wrist orthosis and received advice on hand use at home, with 1 group also receiving 660 nm light at 30 mW and 10 J/cm² for 2 minutes per session, across 12 sessions over 42 days. Total symptom and function scores fell significantly in both groups after 6 weeks. No significant difference appeared between the groups, though 92.3% of the laser group reached a clinically meaningful change in symptom severity against 76.5% of the splint-only group.

This 2014 randomized controlled trial in Iran randomly assigned 44 patients with mild or moderate carpal tunnel syndrome. Both groups wore a wrist splint for 8 weeks, with 1 group also receiving polarized polychromatic light from 480 to 3400 nm at 90 W and 2.4 J/cm², applied perpendicular to the wrist from 10 centimeters away for 8 minutes per session, 3 times a week across 28 days. Pain scores and the timing of the sensory nerve signal improved significantly in both groups. Other nerve measurements did not change in either group, and no meaningful difference in pain emerged between them.

This 2013 randomized controlled trial in Iran randomly divided 50 people with mild or moderate carpal tunnel syndrome into 3 groups. 1 group received 880 nm light at 50 mW and a total of 6 J/cm² across 14 and 70 days alongside a splint, 1 received a sham device alongside a splint, and 1 wore the splint alone. Nerve readings, symptom severity, function, and pain all improved in all 3 groups at 3 weeks and again at 2 months. No significant difference emerged between the 3 groups on any clinical or nerve measure.

When a 2012 randomized controlled trial set 2 laser doses against a placebo, it randomly assigned 60 patients with carpal tunnel syndrome to 3 groups. 1 group received 830 nm light at 50 mW, delivering 1.2 J to each painful point, 1 received 0.6 J per point, and 1 received a placebo, with 5 points along the nerve treated 5 times a week across 15 days. Pain, grip strength, symptom severity, and function all improved significantly from baseline in all 3 groups. Only the 2 active groups improved in sensory nerve speed at the palm, and no outcome differed significantly between the groups.

5 of 21 people given laser alongside a splint reported full recovery, compared with 1 of 24 given the splint alone, in a 2009 randomized controlled trial of 45 people, all with mild or moderate carpal tunnel syndrome (CTS) on one side lasting more than 3 months. 21 received 10 sessions of 830 nm light at 30 mW, delivering 8.1 J for 4.5 minutes per session, alongside a splint, and 24 wore the splint alone, with assessment at the start and after 90 days. The laser group improved significantly on both clinical scores and nerve conduction measures, while the splint group improved only on symptom severity and lost grip strength significantly. The trial noted that the benefit showed in nerve readings rather than in clinical measures.

Neither group outperformed the other in a 2004 randomized controlled trial of low-level laser therapy in Canada. 15 patients aged 34 to 67 were assigned to 7 receiving 860 nm light at 60 mW and 6 J/cm² over the wrist and 8 receiving a sham device, both treated for 30 minutes per session, 3 times a week across 35 days. Symptoms improved significantly in the sham group and in the treated group alike. No measure showed a significant difference between the 2 groups, and the trial concluded that laser was no more effective than sham for this condition.