The Effects of Laser Moxibustion on Knee Osteoarthritis Pain in Rats

Background: Although chronic pain affects the quality of life of patients with osteoarthritis, current medical treatments are either ineffective or have long-term side effects. Recently, low-intensity laser irradiation of corresponding acupoints was demonstrated to alleviate pain. Objective: The aim of the present study was to investigate the effects of 10.6 μm laser moxibustion on a monosodium iodoacetate (MIA)-induced knee osteoarthritis pain model. Methods: Thirty-two rats were randomly assigned to four groups: Saline, MIA, MIA+Laser, and MIA+Sham Laser. The 10.6 μm laser was used to irradiate the ST35 for 10 min once a day for a total of seven applications. The paw withdrawal mechanical threshold and weight-bearing difference were performed to evaluate the analgesic effects of laser moxibustion. At the end of the experiment on days 28, the joint histology, the levels of metalloproteinases-13 (MMP-13) in the cartilage, and TNF-α, IL-1β, and IL-6 in the synovial membrane were measured to determine the chondroprotection and anti-inflammatory effect of laser moxibustion. Results: Early laser moxibustion significantly reversed the MIA-induced mechanical hyperalgesia and weight-bearing difference, especially on the 28th day (p < 0.001). Moreover, laser moxibustion prevented the articular pathological lesions and cartilage destruction on days 28 (p < 0.01). Remarkably, the levels of cartilage MMP-13, and synovial TNF-α, IL-1β, and IL-6 also decreased on day 28 (p < 0.05) after the early treatment of laser moxibustion. Conclusions: 10.6 μm laser moxibustion may have long-lasting analgesic, anti-inflammatory, and chondroprotection effects, suggesting that it may emerge as a potential therapeutic strategy for the chronic pain treatment of osteoarthritis.