Abstract
K
Treatment modalities for osteoarthritis aim to decrease pain and increase range of motion, improving functional independence and quality of life. Photomedicine [earlier terms: low-level laser therapy (LLLT), laser biostimulation, photobiomodulation] is one of the nonpharmacological treatment modalities for the conservative management of osteoarthritis. It was introduced as an alternative treatment for osteoarthritis decades ago, but its beneficial effects are still controversial.
Photomedicine might induce anti-inflammation, inhibiting production of inflammatory mediators. Alves et al. reported that photomedicine (LLLT) was efficient in modulating inflammatory mediators [interleukin (IL)-1β, IL-6] and inflammatory cells (macrophages and neutrophils), which correlated with the histology that showed a reduction in the inflammatory process. 4 Barabás et al. demonstrated that a single diode laser irradiation of the synovial samples of patients with osteoarthritis can statistically significantly alter the expression of some proteins in vitro. 5 Comparative analysis, conducted by dos Santos et al., of two low-level laser doses (doses of 2 and 4 J) on the expression of inflammatory mediators and on neutrophils and macrophages in acute joint inflammation showed that both laser modalities were efficient in reducing cellular inflammation and decreasing the expression of IL-1β and IL-6. 6 There was more reduction in tumor necrosis factor (TNF)-α with a dose of 2 J than with a dose of 4 J. A single application with 2 J was more efficient in modulating inflammatory mediators and inflammatory cells.
In a progressive osteoarthritis rabbit model, Wang et al. demonstrated that photomedicine (LLLT) plays a protective role against cartilage degradation and synovitis. 7 In another study, in a osteoarthritis rat model, Moon et al. used magnetic infrared laser irradiation. They suggested that LLLT with a static magnetic field inhibits cartilage degradation and enhances chondrocyte proliferation. 8
A systematic review and meta-analysis of randomized placebo-controlled trials revealed that LLLT administered with optimal doses in an intensive 2- to 4-week treatment regimen, seemed to offer clinically relevant short-term pain relief in osteoarthritis of the knee. 9 In another systematic review, the clinical effectiveness of LLLT on joint pain was investigated. The review showed that laser therapy on the joint reduced pain in patients. 10
There are recent studies reporting the effects of LLLT on knee osteoarthritis. Hegedus et al. designed a study to examine the pain-relieving effect of LLLT and possible microcirculatory changes measured by thermography in patients with knee osteoarthritis. They showed that LLLT reduced pain in knee osteoarthritis and improved microcirculation in the irradiated area. 11 The effect of LLLT on pain relief and functional performance in patients with chronic knee osteoarthritis was investigated by Alghadir et al. 12 LLLT seemed to be an effective modality for short-term pain relief and functional improvement in patients with chronic knee osteoarthritis. Soleimanpour et al. searched the effect of LLLT on knee osteoarthritis in a prospective study. 13 They concluded that LLLT was effective in reducing pain in knee osteoarthritis.
A randomized double-blind placebo-controlled trial was conducted by Alfredo et al. to estimate the effects of LLLT, in combination with exercises, on pain, function, range of motion, muscular strength, and quality of life in patients with osteoarthritis of the knee. 14 They suggested that LLLT, when associated with exercises, was effective in decreasing pain and improving function in patients with osteoarthritis of the knees.
Keshie et al. compared the effects of LLLT and high-intensity laser therapy (HILT) combined with exercise on pain relief and functional improvement in patients with knee osteoarthritis. 15 They concluded that laser (either LLLT or HILT) combined with exercise was more effective than placebo laser with exercise, whereas the effect of HILT and exercise in combination was much more effective in decreasing pain and increasing functional capacity.
Although many studies using laser therapy have been conducted to decrease pain and improve function, the beneficial effects of photomedicine are still controversial. This is probably because of lacking or heterogeneous data on laser type (HeNe, GaAs, GaAsAl), wavelength (632, 785, 810, 830, 850, 890, 904 nm), laser mode (continuous, pulsed), distance of probe from skin, irradiation points (2–8 points), duration of treatment (20 sec to 7 min), mean power out (30–800 mW), energy density (0.218–48 J cm2), irradiation energy per point (0.13–6 J), spot size (0.028–0.0451 cm2), number of sessions, and site of application of photobiomodulation.
On the other hand, until the last decade, the target tissue for the treatment of knee osteoarthritis was cartilage. Recently, this has been changed, because of new data demonstrating that the pathogenesis involves not only cartilage but also subchondral bone and other soft tissues, including synovial tissue in the joints. 16,17
Do we know the answer to the question of whether photobiomodulation should be used as a drug equivalent? 18 I would say, “not yet.”
However, we already know that when laser is used in optimal dosage with optimal technique, and overtreatment is avoided, laser does not cause any damage to the treated and adjacent tissues. 19
As mentioned by Lanzafame, overselling the attributes and benefits of photobiomodulation must be avoided; our path forward is best paved with careful research and methodical testing of parameters and treatment paradigms, coupled with honest evaluation of the results, both positive and negative. 20