This study is a randomized, single blind, controlled trial. Aim to compare the effectiveness (especially the absorption degree of the synovial effusion measured by B ultrasonic) of the treatment group with the control group. The treatment group was given Xiao zhong fang granules orally and short wave infrared radiation and the control group was given the placebo Xiao zhong fang granules orally and short wave infrared radiation. To evaluate the clinical efficacy of the Chinese medicine in the treatment of the synovial effusion of knee osteoarthritis.

Inclusion Criteria:

• 1) the American Society of Rheumatology established the diagnostic criteria for knee OA in 2001;
• 2) Kellgren/Lawrence score of knee joint grade as I,II and early III.
• 3) According to "Principles of clinical guidance for new drugs of traditional Chinese Medicine ",diagnosed as "Xi Bi Disease".
• 4) Patients with informed consent.
• 5)Blood and urine routine tests, liver and kidney functions, electrocardiogram were normal before recruitment.
• 6) Patients were not treated with NSAIDS drugs or hormone drugs, and no patients were treated with drugs related to this disease at least 2 weeks.

Exclusion Criteria:

• 1)Patients suffer from other rheumatic and metabolic diseases such as gout, rheumatoid arthritis, diabetes and so on.
• 2) Patients with knee joint inflammatory infection, such as suppurative and nonspecific.
• 3)Patients accompanied by traumatic synovitis, Villonodular pigmented synovitis, synovial membrane of the knee is the main lesion.
• 4) Patients with informed consent.
• 5)The color of joint fluid of patients' knees is pink or other color or cloudy; the white blood cell counts > 1000 /mm3 or with crystal in the joint fluid.
• 6)Patients blood RF > 30IU/ml, ESR > 20mm/h, CRP > 10mg/L.
• 7)Patients combined with severe cardiovascular, cerebrovascular, liver, kidney and other primary diseases and mental diseases.