The effect of low-level laser in knee osteoarthritis: a double-blind, randomized, placebo-controlled trial

Abstract

Introduction: Low-level laser therapy (LLLT) is thought to have an analgesic effect as well as a biomodulatory effect on microcirculation. This study was designed to examine the pain-relieving effect of LLLT and possible microcirculatory changes measured by thermography in patients with knee osteoarthritis (KOA).

Materials and methods: Patients with mild or moderate KOA were randomized to receive either LLLT or placebo LLLT. Treatments were delivered twice a week over a period of 4 wk with a diode laser (wavelength 830 nm, continuous wave, power 50 mW) in skin contact at a dose of 6 J/point. The placebo control group was treated with an ineffective probe (power 0.5 mW) of the same appearance. Before examinations and immediately, 2 wk, and 2 mo after completing the therapy, thermography was performed (bilateral comparative thermograph by AGA infrared camera); joint flexion, circumference, and pressure sensitivity were measured; and the visual analogue scale was recorded.

Results: In the group treated with active LLLT, a significant improvement was found in pain (before treatment [BT]: 5.75; 2 mo after treatment : 1.18); circumference (BT: 40.45; AT: 39.86); pressure sensitivity (BT: 2.33; AT: 0.77); and flexion (BT: 105.83; AT: 122.94). In the placebo group, changes in joint flexion and pain were not significant. Thermographic measurements showed at least a 0.5 degrees C increase in temperature--and thus an improvement in circulation compared to the initial values. In the placebo group, these changes did not occur.

Conclusion: Our results show that LLLT reduces pain in KOA and improves microcirculation in the irradiated area.

FIG. 1.

Irradiated points.

FIG. 2.

(a) The effect of laser treatment on joint flexion. Treatment resulted in significant improvement in joint flexion at all times examined. (b) The effect of placebo laser treatment on joint flexion. We observed no significant change from treatment at any of the times examined. AT, after treatment.

FIG. 3.

(a) The effect of laser treatment on pressure sensitivity of the joint. Treatment resulted in significant improvement in joint flexion at all the times examined. (b) The effect of placebo laser treatment on pressure sensitivity of the joint. We observed no significant change from treatment at any of the times examined.

FIG. 4.

(a) The effect of laser treatment on pain in the joint. Treatment resulted in significant improvement in joint flexion at all the times examined. (b) The effect of placebo laser treatment on pain in the joint. We observed no significant change from treatment at any of the times examined.

FIG. 5.

(a) Lateral image of a right knee before eight active low-level laser therapy (LLLT) treatments. White and grey colors represent higher temperatures, greyer and black colors represent colder temperatures. (b) Lateral image of a right knee after eight active LLLT treatments.

FIG. 6.

(a) Medial thermogram of the left knee before eight placebo LLLT treatments. (b) Medial thermogram of the left knee after eight placebo LLLT treatments.

FIG. 7.

(a) Image from posterior–anterior angle before eight treatments of the right knee joint. (b) Image from posterior–anterior angle after eight treatments of the right knee joint.