The Effectiveness of Acupuncture in the Treatment of Frozen Shoulder: A Systematic Review and Meta-Analysis

Frozen shoulder, also known as adhesive capsulitis, is a painful condition that affects between 2% and 5% of the population, being especially common in people around 50 years of age. This condition is characterized by intense pain, stiffness, and progressive limitation of shoulder movements, both active and passive. Pain is often more intense at night, significantly impairing sleep quality and activities of daily living. Frozen shoulder evolves through three distinct phases: the freezing phase (with progressive pain), the frozen phase (with maximum stiffness), and the thawing phase (with gradual improvement).

Although the problem may resolve spontaneously over one to four years, approximately 15% of patients develop long-term disability. Women have a 58% higher risk of developing this condition, and factors such as diabetes, thyroid disease, and local trauma increase the risk of development. Due to the limitations of available conventional treatments, many patients seek complementary therapies such as acupuncture for symptom relief.

This study aimed to scientifically investigate the efficacy of acupuncture in the treatment of frozen shoulder through a systematic review and meta-analysis of controlled trials. Researchers conducted a comprehensive search of four major medical databases — PubMed, Cochrane Library, Embase, and Web of Science — looking for studies published between 1999 and 2020 that compared acupuncture treatments versus other treatments for frozen shoulder. Strict inclusion and exclusion criteria were used, selecting only English-language controlled trials investigating patients with primary adhesive capsulitis. The methodology included two main approaches: manual acupuncture (in which the needles are manipulated manually) and electroacupuncture (in which small electrical currents are applied through the needles).

Control treatments included physical therapy, medications, home exercises, shock wave therapies, and sham acupuncture (placebo). Researchers evaluated three main aspects: pain reduction (measured by the visual analog scale), shoulder function improvement (through standardized questionnaires), and restoration of shoulder range of motion. The quality of the studies was assessed using internationally recognized tools.

The results of the analysis of 13 controlled trials, involving a total of 966 patients with frozen shoulder, demonstrated significant benefits of acupuncture in several areas. For pain control, the meta-analysis of four studies showed significant reduction in pain intensity in patients treated with manual acupuncture compared to control groups, both in the short term (up to 12 weeks) and in the medium term (1.5 to 3 months of follow-up). Pain reduction was consistent, with improvements maintained over time. As for shoulder function, analysis of three studies revealed significant improvement in the functional capacity of patients treated with acupuncture, allowing greater ease in performing everyday activities such as getting dressed, combing hair, or reaching for objects.

Regarding range of motion, acupuncture showed specific benefits for shoulder flexion (raising the arm forward), with significant improvements observed. The most frequently used acupuncture points were Jian Yu (on the shoulder) and Jian Liao (on the posterior part of the shoulder), strategically located near the areas most affected by the inflammation characteristic of frozen shoulder. Both manual acupuncture and electroacupuncture demonstrated efficacy, with some studies suggesting modest advantages of electroacupuncture for certain aspects of treatment.

The clinical implications of these results are promising for patients and health professionals. Acupuncture presents itself as a safe and effective therapeutic option to complement conventional treatment of frozen shoulder, especially considering that this condition often responds in a limited fashion to traditional treatments. The benefits observed include significant pain reduction, improved functional capacity, and partial restoration of shoulder movements. It is important to note that no serious adverse events were reported in the studies analyzed, indicating a favorable safety profile.

For patients suffering from this debilitating condition, acupuncture may offer symptom relief more rapidly than the natural course of the disease, which can take years for complete resolution. The combination of acupuncture with conventional physical therapy can enhance therapeutic outcomes. For health professionals, these findings suggest that acupuncture can be incorporated as part of a multidisciplinary approach in the management of frozen shoulder, offering patients an evidence-based therapeutic alternative.

However, the researchers identified important limitations that should be considered. The main limitation was the methodological quality of the included studies, classified as "very low" according to international criteria for evaluating scientific evidence. Many studies presented problems with patient randomization, lack of adequate blinding (an inherent difficulty in acupuncture studies, since it is difficult to "blind" the acupuncturist), and relatively short follow-up periods. Only three of the 13 studies compared true acupuncture with sham acupuncture, limiting the ability to evaluate specific effects versus placebo effects.

Furthermore, most studies had follow-up of only 1 to 3 months, an insufficient period for a condition that naturally evolves over years. The diversity of assessment instruments used in the different studies also made more comprehensive analyses difficult. The researchers emphasize the urgent need for future studies with greater methodological rigor, larger samples, longer follow-up periods (ideally one year), and adequate comparisons with placebo acupuncture to definitively confirm the efficacy of acupuncture in frozen shoulder and establish standardized treatment protocols.