Acupuncture for the Treatment of Knee Osteoarthritis: An Overview of Systematic Reviews

Knee osteoarthritis is a degenerative condition that affects millions of people worldwide, characterized mainly by pain, movement limitation, and a significant reduction in quality of life. This disease has become one of the leading causes of physical disability globally, particularly with population aging. Conventional treatment of knee osteoarthritis faces important limitations, since there is no definitive cure for the condition. Current therapeutic options focus on pain relief and improvement of joint function and include exercise, anti-inflammatory drugs, intra-articular injections, and, in severe cases, joint replacement surgery.

However, many of these treatments have significant side effects, especially the prolonged use of medications, which can cause gastrointestinal, cardiovascular, and hepatic problems. In this context, acupuncture has emerged as a promising therapeutic alternative — a millennia-old practice of traditional Chinese medicine (中醫) that demonstrates efficacy in pain relief with fewer adverse effects than conventional treatments.

This study aimed primarily to systematically evaluate the available scientific evidence on the efficacy and safety of acupuncture in the treatment of knee osteoarthritis. To this end, the investigators conducted a comprehensive review of previously published systematic reviews and meta-analyses on the topic. The methodology involved an extensive search in eight databases, including four international and four Chinese, from database inception through August 2021. Two independent researchers performed study selection following rigorous inclusion and exclusion criteria.

Only systematic reviews and meta-analyses that analyzed randomized controlled trials comparing acupuncture with other treatments or placebo in patients with clinically or radiographically confirmed knee osteoarthritis were included. Methodologic quality of the studies was assessed using the AMSTAR 2 tool, considered the gold standard for evaluating systematic reviews. The quality of the evidence was analyzed through the GRADE system, which classifies evidence into four levels — high, moderate, low, and very low — considering factors such as risk of bias, inconsistency between studies, imprecision of results, and publication bias.

The results showed that 14 systematic reviews and meta-analyses were included, encompassing a total of 6 to 21 individual studies each, with populations ranging from 500 to 3,552 participants. With respect to efficacy, the evidence suggests that acupuncture demonstrates significant benefits in pain relief and improvement of joint function compared with controls. Specifically, studies showed that acupuncture was more effective than conventional Western medicine across several outcome measures, including efficacy rate and pain scores. Warm acupuncture (a variant that combines acupuncture with moxibustion) showed particular promise when combined with hyaluronic acid injections.

In terms of safety, acupuncture presented a favorable profile, with fewer adverse effects reported compared with conventional pharmacologic treatments. The few side effects reported were generally mild and temporary, such as small hematomas at the needle insertion site. This evidence is particularly relevant given the risks associated with the prolonged use of traditional anti-inflammatories and analgesics.

For patients with knee osteoarthritis, these findings suggest that acupuncture may be considered a valid and safe therapeutic option, especially for those who experience side effects with conventional medications or prefer less invasive approaches. Acupuncture can be used as a complementary treatment or, in some cases, as an alternative to medications, always under appropriate medical supervision. For health professionals, the results indicate that acupuncture should be considered within a multidisciplinary treatment plan for knee osteoarthritis. However, it is important that professionals be aware of the methodologic limitations of the available studies and properly communicate both the benefits and the limitations of the evidence to patients.

Integration of acupuncture into treatment protocols may be particularly valuable for patients who do not respond adequately to conventional treatments or who have contraindications to medications.

Despite the promising results, this study identified significant limitations in the methodologic quality of the systematic reviews analyzed. Using the AMSTAR 2 tool, all 14 included studies were classified as having "critically low" methodologic quality. The main problems identified included the lack of pre-registered protocols, absence of lists of excluded studies with justifications, lack of information on funding sources, and inadequate explanations of the types of studies included. As to the quality of the evidence, the GRADE system showed that of the 46 outcome measures analyzed, 25 were classified as "very low" quality evidence, 17 as "low," only 4 as "moderate," and none as "high quality." The main factors that lowered the quality of evidence were publication bias and imprecision of the results, followed by inconsistencies between studies and methodologic limitations.

These deficiencies significantly limit the reliability of the conclusions and highlight the need for higher methodologic quality studies in the future.

In conclusion, although the current evidence suggests that acupuncture is an effective and safe therapy for knee osteoarthritis, the methodologic and evidentiary deficiencies of the included studies limit the reliability of these conclusions. Patients may consider acupuncture as a promising complementary therapeutic option, especially those who seek alternatives to conventional treatments or who experience significant side effects with medications. However, it is essential that future research adopt more rigorous methodologic standards, including pre-registration of protocols, more comprehensive literature searches, more careful assessment of study quality, and transparent reporting of conflicts of interest and funding sources. Only through high-quality methodologic studies will it be possible to establish more definitive recommendations regarding the role of acupuncture in the treatment of knee osteoarthritis, providing patients and health professionals with more solid evidence to guide therapeutic decisions.