Is Light Therapy Effective for Shoulder Tendinopathy?
Yes. This comparative study of 75 adults with rotator cuff tendinopathy found that LED photobiomodulation added to therapeutic ultrasound improved pain and function more than ultrasound alone, and infrared LED at 850 nm combined with ultrasound was the best of the five treatments tested.
Photobiomodulation, also called low-level laser therapy, delivers red or near-infrared light to tissue. In this trial it was delivered with LEDs rather than lasers, either on its own or before a session of therapeutic ultrasound.
The patients were aged 45 to 70 and were treated for shoulder tendinopathy. The question the investigators asked was straightforward: does adding light to a standard ultrasound protocol change the result, and does the wavelength matter?
What the Research Shows
The study assessed 75 patients aged 45 to 70 with shoulder tendinopathy, divided into five groups of 15 patients each: ultrasound alone, infrared LED alone (850 nm), visible red LED alone (640 nm), infrared LED combined with ultrasound, and red LED combined with ultrasound. The LED protocols used 3 treatment points at 7.5 joules per point, with the infrared LED at 750 mW for 10 seconds and the red LED at 250 mW for 30 seconds. Ultrasound was 1 MHz at 0.5 W/cm2 with a 100 Hz repetition rate, applied for 4 minutes per session. In the combined groups the light came first, then the ultrasound. Everyone received 12 sessions over 4 weeks.
Twelve parameters were measured: quality of life on the Health Assessment Questionnaire, pain intensity on a visual analog scale, six shoulder ranges of motion, muscle strength in abduction and lateral rotation, and electromyography for abduction and lateral rotation. All five therapies significantly improved every parameter after treatment. Compared against ultrasound alone, infrared plus ultrasound was superior on all 12 parameters. Red light plus ultrasound was superior on 10, infrared alone on 9, and red light alone on 7 (p < 0.05).
Dr. Kumar’s Take
Shoulder pain from tendinopathy can be miserable and persistent, and the standard physical therapy course often feels slow to the patient sitting in front of me. This trial says something useful: light on top of ultrasound beat ultrasound alone, and the infrared arm beat the red arm on the count of parameters improved. That fits how I think about the rotator cuff, which sits under skin, fat, and deltoid, so wavelength and penetration depth are not trivial details.
Practical Takeaways
- Infrared LED at 850 nm combined with therapeutic ultrasound outperformed ultrasound alone on all 12 measured parameters.
- Infrared beat visible red light on this comparison: 850 nm alone exceeded ultrasound on 9 parameters, 640 nm alone on 7.
- All five treatments, including ultrasound alone, improved every parameter measured.
- The protocol was 12 sessions over 4 weeks, so this is a course of treatment, not a single visit.
- Ask your physical therapist about incorporating LED photobiomodulation into your shoulder rehabilitation program.
FAQs
Can I treat my shoulder pain with a home LED device?
Home LED devices are available in the infrared range used here, around 850 nm. The trial used 750 mW infrared LEDs delivering 7.5 joules at each of 3 points, so output power and dose matter, not just the wavelength printed on the box. Position the device as close to the shoulder as possible, and expect a lower-power device to need longer exposure times to deliver the same energy.
How many sessions are needed for shoulder tendinopathy?
In this study the course was 12 sessions over 4 weeks, and improvements were measured after that full course. Consistency over several weeks matters for tendon conditions, which heal slowly because of their limited blood supply.
Why did infrared light work better than red light for the shoulder?
The trial itself does not answer the mechanism, it only reports that infrared came out ahead on the number of parameters improved. My reading is anatomical: the rotator cuff tendons sit beneath skin, fat, and muscle, and near-infrared light at 850 nm reaches deeper tissue than visible red at 640 nm. For a target that deep, I would choose the infrared wavelength.
Bottom Line
Adding LED photobiomodulation to therapeutic ultrasound improved pain, quality of life, shoulder range of motion, and muscle strength more than ultrasound by itself, and infrared at 850 nm was the strongest of the combinations tested. This was a small trial with 15 patients per group, but the intervention is noninvasive and easy to add to an existing physical therapy program.
