Knee osteoarthritis (KOA), also called degenerative knee disease, is one of the most common bone and joint diseases in clinic. It often occurs in middle-aged people, especially women. It was estimated to affect more than 9 million individuals in the United States in 2005 and is a leading cause of disability and medical costs. Most elderly people over the age of 65 have radiographic and/or clinical evidence of osteoarthritis. KOA is a lifelong disease which can lead to obvious pain, joint stiffness, limitation of activity and even joint failure or disability.According to the papers published in the past years, we find that acupuncture therapy for the treatment of knee osteoarthritis include manual acupuncture, electro-acupuncture, acupotomy, laser acupuncture, fire needle and so on, among which manual acupuncture and electro-acupuncture are most commonly used.The aim of this study is to compare the effectiveness of electro-acupuncture and manual acupuncture in reducing pain and improving function in patients with KOA.

Participants will be randomly allocated to one of two groups. Those in the first group receive electro-acupuncture, which involves having needles inserted into acupuncture points (locations on the body affected by acupuncture) which are stimulated manually for 10 seconds to create "De Qi" sensation and an electrical apparatus (HANS-200A acupoint nerve stimulator, Nanjing Jisheng Medical Co., Ltd. production, wave of 2/100Hz) was then connected to the needles with alligator clips to stimulate the needles in pairs ST36-SP9/GB34 and ST34-SP10. The stimulus intensity will be increased until the patient reported a strong but comfortable intensity. Those in the second group have the same schedule as the electro-acupuncture group except that the electrical apparatus has working power indicator and sound without actual current output. Both groups will receive 30-minute, 24 sessions intervention over eight weeks. Moreover, a number of questionnaires at the start of the study and then again after 4, 8, 12 and 16 week will be completed by participants.

It is expected that participants will benefit from a decrease in pain and improved function. The risks of participation are minimal. Occasionally, acupuncture can make people feel nauseous or experience a temporary increase in pain either during or after treatment. Rare side effects during acupuncture treatment include fainting, infection and subcutaneous hematoma (pooling of blood under the skin). Participants will be warned of these potential side-effects before consenting to have acupuncture.

Participants will be allowed, or required, to withdraw from the trial based on the following:

1. A major protocol violation;
2. Development of a serious disease preventing continuation in the trial;
3. Adverse events related to acupuncture;
4. Request to be withdrawn from the trial. The purpose is to accumulate clinical data, obtain the outcome data of the intervention method and prove the feasibility of the study protocol. Sixty patients will be selected as the sample size according to clinical experience.

Inclusion Criteria:

• Age 45-75 years old, male or female
• Single / bilateral knee pain, duration of more than 6 months
• KL (Kellgren-Lawrence) grade Ⅱ or Ⅲ
• VAS ≥ 40mm
• Signed informed consent

Exclusion Criteria:

• Surgery history of knee or waiting for surgery (knee replacement or knee arthroscopy)
• History of arthroscopy within 1 year or intra-articular injection within 4 months
• Knee pain caused by other diseases (such as joint bodies, severe effusion of joint cavity, infection, malignant tumors, autoimmune diseases, trauma, etc.)
• Severe acute/chronic organic or mental diseases
• Coagulation disorders (such as hemophilia, etc.)
• Pregnant women, pregnant and lactating women
• History of receiving acupuncture or massage treatment within one month
• Participation in another clinical study in the past 3 months
• With a cardiac pacemaker, metal allergy or needle phobia