In this proposal, we plan to dynamically investigate brain response to verum acupuncture (of two different "doses") and placebo acupuncture, using a paradigm that approximates clinical acupuncture practice across multiple treatment sessions in knee osteoarthritis (OA) patients. This proposal aims to: 1) characterize session-to-session brain responses to verum / sham acupuncture treatment (reliability of response) for OA patients, and 2) investigate how different "doses" of acupuncture influence brain response and acupuncture efficacy (impact of dose). The findings of this project will deepen our biological understanding on why and how acupuncture can treat chronic pain and what happens in the brain during the multiple-session acupuncture treatment.

Inclusion Criteria:

1. Volunteers 40-70 years of age.
2. Meet the Classification Criteria of the American College of Rheumatology for osteoarthritis of the left / right knee for at least the past 3 months, as determined by the referring physician.
3. Radiographic evidence of Grade 2 or 3 knee OA using the Kellgren-Lawrence Scale [78, 85-87].
4. Patients must have moderate or greater clinically significant pain on most days during the past month (more than 15 days out of 30, of average daily pain of >3/10) in the left or right knee.
5. At least a 10th grade English-reading level; English can be a second language provided that the patients feel they understand all the questions used in the assessment measures.

Exclusion Criteria:

1. Any interventional procedure for knee pain, including corticosteroid injections (within 6 months, [88]) to the knee.
2. Prior acupuncture treatment for any condition. Because we are using a placebo needle as a control, acupuncture-naive patients are necessary to maximize the benefits of blinding and to control expectancy.
3. The intent to undergo surgery during the time of involvement in the study.
4. Presence of any illness or medication use that is judged to interfere with the trial. For example: skin irritations around the knee such as psoriasis; bleeding disorders or anticoagulant use that would be contraindications for acupuncture; opioids or benzodiazepines, which may alter pain sensitivity and BOLD response.
5. Knee pain due to other causes, such as inflammation or malignancy, other pain disorders that may refer pain to the leg, OA of ipsilateral hip, diagnosis of RA.
6. Non-ambulatory status.
7. History of cardiac, respiratory, or nervous system disease that, in the investigator's judgment, precludes participation in the study because of a heightened potential for adverse outcome. For example: asthma or claustrophobia.
8. Presence of any contraindications to fMRI scanning. For example: cardiac pacemaker, metal implants, fear of closed spaces, pregnancy.

Limitations of the study are the small sample size as well as the effects of factors such as age, gender, and chronic duration of pain.