Osteoarthritis of the knee is a major cause of disability among adults. Treatment is focused on symptom management, with nonpharmacologic therapies being the preferred first line of treatment. Acupuncture is considered a potentially useful treatment for osteoarthritis. The objective of this article is to review the English-language articles, indexed in MEDLINE or CINAHL, describing randomized, controlled trials of the effects of needle or electroacupuncture on knee osteoarthritis. Ten trials representing 1456 participants met the inclusion criteria and were analyzed. These studies provide evidence that acupuncture is an effective treatment for pain and physical dysfunction associated with osteoarthritis of the knee.