Therapeutic Potential of Acupuncture in Knee Osteoarthritis: Clinical Efficacy and Mechanistic Insights

Knee osteoarthritis (KOA) is one of the most common musculoskeletal conditions in the world, affecting approximately 654 million people globally. This degenerative joint disease causes chronic pain, stiffness, and functional limitation that can significantly compromise patients' quality of life. Characterized by progressive degradation of articular cartilage, inflammation of the synovial membrane, and changes in subchondral bone, KOA results from a complex interaction between mechanical, inflammatory, and metabolic factors. The prevalence of the condition increases with age, being more common in people over 45 years, and predominantly affects women, with a rate 1.8 times higher than in men.

Conventional treatments include anti-inflammatory medications and, in advanced cases, joint replacement surgery. However, these approaches have important limitations, including significant adverse effects, high costs, and surgical risks. In this context, acupuncture has emerged as a promising therapeutic alternative, offering a non-pharmacological and minimally invasive approach to the management of KOA.

This study aimed to systematically evaluate the clinical efficacy of acupuncture in the treatment of knee osteoarthritis and to investigate the biological mechanisms underlying its therapeutic effects. The researchers conducted a comprehensive narrative review that examined both clinical and mechanistic evidence on different acupuncture modalities. To this end, they performed a systematic search of multiple databases, including PubMed, CNKI, and Google Scholar, covering publications from 1994 to 2024. The methodology involved analysis of 21 randomized controlled clinical trials investigating the efficacy of acupuncture, in addition to mechanistic research exploring the biological processes involved.

The selected studies encompassed 3,176 patients with KOA, ages 30 to 91 years, using various acupuncture modalities, including manual acupuncture, electroacupuncture, warm needling, and combined techniques. Evaluation criteria included standardized scales such as the Visual Analog Scale (VAS), the WOMAC Index (Western Ontario and McMaster Universities Osteoarthritis Index), and quality of life questionnaires.

Results from clinical studies demonstrated that acupuncture as monotherapy produced substantial benefits for patients with KOA. The analysis revealed significant reductions in pain intensity, with VAS decreases ranging from 32% to 54% compared to control groups. Functional scores also showed notable improvements, with WOMAC increases of 25% to 40%, indicating improved joint function and reduced stiffness. Furthermore, when acupuncture was combined with other modalities such as moxibustion or electroacupuncture, even more pronounced synergistic effects were observed.

Electroacupuncture, in particular, proved superior to conventional manual acupuncture in some parameters, especially in reducing inflammatory mediators. The studies also documented improvements in patients' quality of life, measured by the SF-36 questionnaire, and reductions in associated symptoms such as anxiety and depression related to chronic pain.

From a mechanistic standpoint, the research revealed that acupuncture acts through multiple biological pathways to combat KOA. At the cellular and molecular level, treatment demonstrated the ability to modulate the inflammatory response through inhibition of pro-inflammatory pathways mediated by nuclear factor kappa B (NF-κB), resulting in decreased inflammatory cytokines such as IL-1β, TNF-α, and IL-6. Simultaneously, it promotes an increase in anti-inflammatory factors such as IL-10. Acupuncture also influences macrophage balance, promoting polarization of M1 macrophages (pro-inflammatory) toward M2 (anti-inflammatory).

Regarding cartilage protection, studies showed that acupuncture inhibits chondrocyte apoptosis (cell death) through regulation of proteins such as caspase-3, while activating protective autophagy processes via Pink1-Parkin and LC3-II/Beclin-1 pathways. Treatment also demonstrated the ability to rebalance cartilage metabolism, increasing the synthesis of important components such as aggrecan and type II collagen, while inhibiting degradative enzymes such as MMP-13. For pain control, acupuncture modulates both peripheral and central sensitization, activating μ (mu) opioid receptors and descending pain inhibition systems in the central nervous system.

The clinical implications of these findings are significant for both patients and healthcare professionals. For patients with KOA, acupuncture offers a safe and effective alternative to conventional treatments, with minimal adverse effects and the ability to provide lasting pain relief and functional improvement. The treatment may be particularly beneficial for patients who do not tolerate anti-inflammatory medications well or who wish to avoid surgical interventions. The multimodal nature of acupuncture's effects — combining symptomatic relief with structural joint protection — suggests it may not only treat existing symptoms but also slow disease progression.

For healthcare professionals, these results provide robust scientific evidence supporting the inclusion of acupuncture in integrative treatment protocols for KOA. Understanding the mechanisms of action allows for a more targeted and personalized application of treatment, optimizing clinical outcomes.

Although the results are promising, the study acknowledges several important limitations that must be considered. Heterogeneity in the acupuncture protocols used across studies — including variations in point selection, needle manipulation techniques, and treatment frequency — makes direct comparisons and synthesis of findings difficult. Efficacy assessment was based primarily on subjective measures such as pain scales, with limited use of objective biomarkers or structural imaging techniques to evaluate changes in joint cartilage. Furthermore, the lack of adequate placebo controls in some studies and the scarcity of long-term follow-up data limit the complete validation of sustained acupuncture efficacy.

The mechanistic connection between symptom relief and prevention of disease progression also requires additional investigation.

In conclusion, this review establishes acupuncture as a scientifically grounded therapeutic intervention for the treatment of knee osteoarthritis, offering a non-pharmacological approach that combines clinical efficacy with safety. The multiple and complementary mechanisms of action — from inflammation modulation to neuroplasticity — provide a solid foundation for its integration into comprehensive treatment strategies. Future studies should focus on standardizing protocols, validating mechanistic findings in human popula