PT Classroom - Low Level Laser Therapy: Therapeutic Theories, Clinical Uses, and the Evidence ׀ by Jennifer Werwie, DPT


Jennifer Werwie, DPT, graduated with her Doctor of Physical Therapy degree from the University of Wisconsin-Madison. She received her BS degree in Kinesiology-Exercise Science from UW-Madison in 2008. Jennifer is also a certified personal trainer and fitness instructor. She is a Kenosha native and is an employee with United Hospital System where she primarily works in the outpatient PT setting.

 Low Level Laser Therapy: Therapeutic Theories,

Clinical Uses, and the Evidence


The theoretical foundations of laser were first born back in the early 20th century with Albert Einstein's “Quantum Theory of Radiation”(1). That has transpired over the years, and today, almost every section of modern society has found a use for laser technology: barcode scanners, laser printers, laser light shows, forensic fingerprint identification, and even electro-optical countermeasures in the military to name a few. The word, laser, actually originated as an acronym for "Light Amplification by Stimulated Emission of Radiation” (1). And the use of laser in the medical world has erupted in the past couple decades with the laser scalpel, LASIK eye surgery, laser angioplasty, and laser-assisted cosmetic and dental treatments (2).

But what do we know about the use of laser light treatment in the physical therapy realm? Low level laser therapy, or LLLT, has found a place as an adjunctive therapeutic approach for a variety of both acute and chronic musculoskeletal conditions. LLLT is a noninvasive, laser light source treatment that acts via a single wavelength to produce non-thermal therapeutic effects (3). There is no heat, sound or vibration involved. Instead, it is theorized that low level laser therapy acts at the cellular level via varying physiological mechanisms to produce several therapeutic effects (3, 4):

1. Increased ATP production and oxygen consumption (promotes healing effects)
2. Increased production of serotonin and endorphins (pain inhibitory effects)
3. Reduced prostaglandin synthesis (increased anti-inflammatory effects)
4. Increase in blood circulation to the skin
5. Decrease membrane permeability for Na+/K+ in nerve cells (causes hyperpolarization)
6. Increased lymphatic flow and decreased edema

Because of the wide variety of conditions that LLLT is used to treat, there is much variance in treatment parameters such as altering pulse rate, applicator placement, wavelength, irradiance (power/unit area), beam divergence, spot size, delivery (fiber optic, direct), polarity, pulse duration, and duty cycle (3). The two main types of laser devices fall in the categories of Super Pulsed or Continuous Wave lasers. With Super Pulsed, the power density is greater and the therapeutic dosage is smaller. Continuous Wave lasers have a lower power density and thus require larger therapeutic dosages. Dosage parameters also vary based on the goal of main therapeutic effect: tissue repair or pain inhibition. The following chart displays dosage guidelines of varying energy densities (measured in J/cm²) from the World Association of Laser Therapy (WALT) (5).


LLLT has been used in physical therapy clinics for a wide range of conditions such tendinopathies and joint disorders, osteoarthritis, ankle sprains, carpal tunnel syndrome, low back pain, lateral and medial epicondylities, and even venous and decubitus ulcers (6-9). Even though LLLT is being increasingly utilized in therapy settings across the country, all evidence for its therapeutic use are either in the investigational or theorized stages. This is simply due to the fact that studies have lacked strong external validity with their small sample sizes, lack of internal consistency across studies(wide range of treatment parameters), and lack of comparing LLLT to alternative therapies (3). Due to this lack of established evidence, a good majority of insurance companies still consider LLLT as experimental and investigational, and do not cover the treatment. However, this has not halted many therapy clinics from employing LLLT treatments with the recent fee-for-service model. According to a recent article in The Washington Post, "a laser device costs approximately $4000, while each treatment costs from $25 to $50 with a typical course of treatment involving 10 to 15 sessions over time (3,8)".

Evidence-based practice is based on three central tenets: research/evidence, clinician experience/expertise, and patient preference. So although LLLT has yet to fully prove itself in the realm of research, there is no doubting that many physical therapists are finding its use efficacious in their practice. And with patient-centered care on the forefront of medicine now more than ever, clinicians are taking patient response and preference to heart. As an adjunctive, noninvasive and versatile treatment approach, low level laser therapy may just be a worthwhile addition to the rehabilitation toolbox.


Last revised: October 21, 2012
by Jennifer Werwie, DPT

1) “Laser.” Wikipedia encyclopedia: Sept 2001. Last updated: Oct 15, 2012.
2) “Lasers; Chapter 5: The Medical Uses of Laser.” 2010. Science Clarified.
3) Wang, Grace. Low Level Laser Therapy (LLLT). Technology Assessment. May 2004. Office of Medical Director: Department of Labor & Industries.
4) ADVANCE Physical Therapy and Rehab. “Effective Treatment Strategies for Low-Level Laser Therapy.”ADVANCE News Magazines. 2012 Merian Matters.

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