Compared with patients with knee osteoarthritis treated with physical therapy and anti-inflammatory drugs alone, patients who also received TCA or sham acupuncture had improvements in pain at 26 weeks. Surprisingly, the researchers found no difference in pain reduction between real and fake acupuncture. Several potential explanations are possible. First, because of psychological effects, patients who know they are getting special types of treatment report feeling better regardless of whether the treatment really works. Second, patients who received acupuncture had more intense contact with health care providers, which could explain why they felt better. Third, sticking needles into the body may have a physical effect on pain, regardless of whether the needles are placed according to TCA principles.