Acupuncture-Related Therapy for Knee Osteoarthritis: A Narrative Review of Neuroimaging Studies

Knee osteoarthritis is one of the most common joint conditions worldwide, affecting approximately 30% of people over 45 years of age. Characterized by progressive loss of articular cartilage, this condition causes intense pain and significant functional limitations, dramatically impacting patients' quality of life. In addition to the physical suffering, knee osteoarthritis is associated with an increased risk of mortality and represents a major economic burden, with direct medical costs exceeding ten thousand dollars per patient over a lifetime. Faced with this scenario, the search for effective treatments has led many patients and healthcare professionals to explore complementary therapies.

Acupuncture, an ancient practice of Traditional Chinese Medicine, has gained growing recognition and is officially recommended by treatment guidelines for the management of knee osteoarthritis symptoms.

The study in question had as its primary objective to analyze how acupuncture and related therapies, such as moxibustion, affect brain function in patients with knee osteoarthritis. The researchers conducted a systematic narrative review, examining studies that used neuroimaging techniques to investigate brain responses to these therapies. The search was conducted across multiple scientific databases, both in English and Chinese, covering publications from the start of records through October 2023. From the 312 articles initially identified, thirteen studies were considered eligible and included in the final analysis.

These studies involved a total of 561 patients with knee osteoarthritis and 131 healthy individuals, with ages ranging from 40 to 69 years. Most studies used functional magnetic resonance imaging to map brain activity, while ten studies focused specifically on acupuncture and three on moxibustion.

The results revealed fascinating discoveries about how these therapies influence the brain. Acupuncture demonstrated the capacity to regulate several brain regions important for pain processing, including the prefrontal cortex, anterior cingulate cortex, insula, thalamus, and hippocampus. These areas are part of two fundamental brain systems: the medial pain system and the limbic system. The medial pain system is responsible for the cognitive and emotional aspects of pain, while the limbic system regulates emotional and motivational responses.

The studies showed that acupuncture can improve connectivity between these brain regions, especially between the prefrontal cortex and other areas involved in pain control. Particularly interesting was the finding that real acupuncture produced more extensive and significant brain responses compared with sham acupuncture, providing scientific evidence that the therapeutic effect goes beyond a simple placebo effect. Moxibustion, in turn, demonstrated an even broader activation pattern, affecting not only regions related to pain but also the cerebellum, white and gray matter, and other brain areas.

For patients, these findings offer a solid scientific explanation for why acupuncture can be effective in treating knee osteoarthritis pain. The fact that these therapies can modify the activity of specific brain regions involved in pain processing suggests that the clinically observed benefits have a real neurobiological basis. This is particularly relevant because chronic osteoarthritis pain affects not only the joints but also alters brain function, creating a cycle of persistent pain. Acupuncture's ability to restore normal patterns of brain activity may explain not only pain reduction but also improvements in mood, cognitive function, and patients' overall quality of life.

For healthcare professionals, these findings provide robust scientific evidence that can guide treatment decisions and help integrate acupuncture more effectively into therapeutic plans. The identification of specific brain regions that respond to treatment can also help predict which patients are most likely to benefit from the therapy.

Despite the promising results, the study has some important limitations that should be considered. Most of the included studies had a relatively small number of participants, which may limit the generalizability of the results. In addition, there were significant variations in the acupuncture protocols used, including different acupoints, session durations, and number of treatments, making it difficult to determine the most effective protocol. The methodological quality assessment revealed that several studies presented "some concerns" regarding risk of bias, mainly due to the difficulty of adequately blinding acupuncture practitioners and, in some cases, assessors.

The researchers also identified the need for more studies investigating long-term structural effects on the brain and directly comparing different treatment modalities. Future research should also explore the relationship between the amount of acupuncture stimulation and changes in brain activity, as well as investigate individual differences in treatment response. In conclusion, this study represents a significant advance in understanding the brain mechanisms by which acupuncture provides pain relief in knee osteoarthritis, offering a solid scientific basis for its clinical use and opening pathways for future investigations that may further optimize these treatments.