According to BMC Musculoskeletal Disorders 2009, 10:130

From the GP database of 15,927 patients, 335 potential trial participants were identified and invited to participate. After screening responses, 78 (23%) were identified as eligible and 30 patients who responded most promptly were randomised to 'acupuncture plus usual care' (15 patients) and 'usual care' alone (15 patients). Attendance for acupuncture appointments was high at 90% of the maximum. Although the trial was not powered to detect significant changes in outcome, the WOMAC pain index showed a statistically significant reduction at 3 months in the acupuncture group compared to usual care. This was not sustained at 12 months. The sample size for a fully powered two-arm trial was estimated to be 350. .

Conclusions
This pilot study provided the evidence that a fully powered study to explore the longer term impact of acupuncture would be worthwhile, and relevant design features for such a trial were determined.

Thanks to scientist's contribution.