Clinical effect and contributing factors of acupuncture for knee osteoarthritis: a systematic review and pairwise and exploratory network meta-analysis

Knee osteoarthritis is one of the most common conditions affecting the joints, causing chronic pain, stiffness, and restricted movement that significantly impact patients' quality of life. This degenerative condition affects approximately 3.8% of the global population and accounts for about 85% of all osteoarthritis cases. For many people, symptoms interfere with daily activities and may even increase the risk of mortality by limiting mobility and overall well-being.

Traditional treatment for knee osteoarthritis often includes nonsteroidal anti-inflammatory drugs, but these can cause significant side effects, especially cardiovascular and gastrointestinal problems. Given these limitations and the growing need for safe and effective alternatives, acupuncture has been considered a promising therapeutic option. However, current medical guidelines provide conflicting recommendations regarding its use, and it remained unclear which type of acupuncture would be most effective or what the optimal dose would be for the best results.

This study aimed to clarify these important questions through a comprehensive systematic review and meta-analysis that included 80 controlled clinical trials involving 9,933 patients. The researchers analyzed data from eight different scientific databases, covering publications from inception through November 2023. The study compared the efficacy of acupuncture with several other treatments, including sham acupuncture (placebo), anti-inflammatory drugs, usual care, intra-articular injections, and control groups. Two main types of acupuncture were assessed: traditional manual acupuncture and electroacupuncture, which uses electrical stimulation in addition to the needles.

The researchers also developed a scoring system to classify the acupuncture "dose," considering factors such as the number of points used, intensity of stimulation, frequency of sessions, and treatment duration. Based on this analysis, treatments were classified as high, moderate, or low dose. The primary objective was to measure pain reduction, while secondary objectives included improvements in physical function and quality of life.

The results revealed important and encouraging findings for patients suffering from knee osteoarthritis. Acupuncture proved to be significantly more effective than sham acupuncture in reducing pain, with an improvement corresponding to approximately 18.5 points on a 100-point pain scale. This improvement is considered clinically significant — that is, a difference that patients can actually feel in their daily lives. In addition, acupuncture also proved superior to conventional anti-inflammatory medications, usual care, and control groups, both for pain reduction and improvement of physical function.

A particularly interesting finding was that electroacupuncture showed superior results compared with traditional manual acupuncture. Electroacupuncture combines needle insertion with mild electrical stimulation, providing a more intense stimulus to acupuncture points. This technique showed greater efficacy in reducing pain compared with manual acupuncture. Regarding treatment dose, the researchers found evidence that higher doses of acupuncture tend to produce better results, especially when compared with anti-inflammatory medications.

Regarding safety, acupuncture was generally safe, with few serious adverse events reported. Although there was a small increase in the risk of serious adverse events compared with sham acupuncture, this risk remained low and the events were not considered to be related to the acupuncture treatment itself.

The clinical implications of these findings are substantial for both patients and health care professionals. For patients suffering from knee osteoarthritis, especially those who cannot use anti-inflammatory medications due to stomach, heart, or other side effects, acupuncture emerges as a valid and effective therapeutic alternative. The results suggest that electroacupuncture may be preferable to manual acupuncture and that treatments with adequate doses tend to produce better outcomes. For health care professionals, these findings provide important evidence to guide treatment decisions and discussions with patients about therapeutic options.

The study also indicates that current medical guidelines, which provide conflicting recommendations regarding acupuncture for knee osteoarthritis, may need to be reconsidered in light of this evidence. The results support the inclusion of acupuncture, particularly electroacupuncture, as a legitimate treatment option for patients with this condition.

However, it is important to acknowledge the study's limitations. The overall quality of the included studies was rated low, mainly because many trials were unable to apply adequate blinding techniques — that is, patients knew whether they were receiving real or sham acupuncture. In addition, there was significant variability across studies in terms of techniques used, number of sessions, and other factors, making the results less precise. The long-term effects of acupuncture also remain uncertain, since few studies followed patients for extended periods.

In conclusion, although the results are promising and suggest that acupuncture may offer clinically important benefits for patients with knee osteoarthritis, the quality of the available evidence remains limited. Electroacupuncture and higher treatment doses appear to be factors that contribute to better outcomes, but more high-quality studies are needed to confirm these findings. Patients interested in acupuncture should discuss this option with their physicians, considering both the potential benefits and the limitations of the current evidence. The field needs more rigorous research to establish optimal treatment protocols and confirm the long-term efficacy of this promising therapy.