NEW YORK (Reuters Health) - Acupuncture may help bring lasting pain relief to people with osteoarthritis of the hip or knee, researchers reported Monday.

In a study of more than 3,600 adults with knee or hip arthritis, German researchers found that those who had acupuncture added to their usual treatment showed a greater improvements in pain, stiffness and joint function.

What's more, the benefits were still there three months after patients' last acupuncture session, the study authors report in the journal Arthritis & Rheumatism.

Along with past research, the findings offer enough evidence to recommend acupuncture for knee and hip osteoarthritis, said lead study author Dr. Claudia M. Witt of Charite University Medical Center in Berlin.

Acupuncture has been widely used to treat various musculoskeletal disorders, and other chronic pain conditions. Scientists speculate that acupuncture may alter signals in nerve cells or affect the release of various pain-related chemicals of the central nervous system.

This latest study followed 3,633 older adults with either knee or hip arthritis. There were 712 patients who were randomly assigned to either remain on their standard treatment or to have acupuncture added to their regimen for three months. The rest of the study participants did not want to be randomly assigned to a group and were allowed to have acupuncture.

All of the patients completed a standard questionnaire on arthritis pain, stiffness and disability at the start of the study, then again three and six months later.

After three months of therapy, Witt's team found that the acupuncture patients showed an improvement in their questionnaire scores on average, while the comparison group remained unchanged. About one third of the acupuncture group had an improvement of 50 percent or more. The benefits were still apparent three months after their last acupuncture treatment.

The study is one of the largest clinical trials of acupuncture to date. Based in part on the findings, the German government is considering a proposal to cover acupuncture under its health system, Witt and her colleagues note.

Patients in the study received their acupuncture from a doctor, Witt told Reuters Health. However, she added, studies in the U.S. have found therapy delivered by acupuncturists to also be effective for chronic pain.

"The most important point," Witt said, "is that the professional who provides the acupuncture treatment is well educated and experienced."