Shedding light on laser therapy for musculoskeletal disorders

laser therapy as a medical intervention has been in use or under investigation for more than 40 years. But whether these treatments are fruitful or futile remains a topic of discussion—a conversation that starts by scrutinizing the state of the science. Low-level laser therapy—or cold laser therapy—is categorized into three classes based on wattage and hazard potential, ranging from less than 1 milliwatt (Classes I and II) to 500 milliwatts (Class III). These lasers generate light in a single wavelength, with output strong enough to penetrate only a few millimeters into the tissue and musculoskeletal structures, akin to the effect of holding a flashlight to your hand. Newer lasers are available that operate at a much higher power, termed Class IV devices. Because these are powered up to 10 watts and can penetrate approximately 4 inches (10 centimeters) deep, they are applied in a pulsing manner rather than continuously to reduce the likelihood of damage to skin and blood vessels. For use in physical medicine and rehabilitation, these highpowered lasers have been deployed and studied only in the past five years.