This study evaluates the safety and efficacy of investigational products in the treatment of knee Osteoarthritis. Half of participants will receive medical chitosan, while the other half will receive sodium hyaluronate.

Medical chitosan and sodium hyaluronate each form the reticular layer to cover the joint surface, alleviate the joint friction and pain. For medical chitosan, its half-life is longer than sodium hyaluronate, so the interval time of intra-articular injection is longer.

Inclusion Criteria:

1. Males or females at the age of 40-75 years old

2. Conforming to the diagnosis standard of the American College of Rheumatology in 2009： knee pain and osteophyte determined with X-ray, and at least one of the following items：

   • above 50 years old
   • morning stiffness less than 30 minutes
   • knee joint with fricative when moving

3. The studying knee has score of 40-90 mm on a 100 mm measured VAS and the other side was less than 40mm when walking on flat ground.

4. The studying knee has score of 1, 2 or 3 determined by radiological Kellgren-Lawrence grading scale.

5. Patients who have treatment requirements and can obey the therapeutic schedule

6. Body mass index(BMI) ≤35kg/m2。

7. Able to follow the clinical observation and follow up.

8. The subjects are able to understand and sign the informed consent after fully understand this study, the disease, investigational drugs, the therapeutic schedule and the potential risks.

Exclusion Criteria:

1. Positive signs of swelling or floating patella test，and there are obvious effusion of knee joint in clinical.
2. Other inflammatory pain diseases of knee joint, such as rheumatism/ rheumatoid arthritis, psoriatic arthritis, gout, hemophilic arthritis, etc.
3. Pain diseases of knee joint, except for osteoarthritis, such as intra-articular tumor, villonodular synovitis, joint trauma, etc.
4. Pregnant or lactating females.
5. Participants who suffer from serious cardiovascular disease (Sudden cerebral infarction with sequela or myocardial infarction within recent 6 months), hepatic disease, kidney disease；Participants whose ALT and AST are twice or more than twice than that of the upper limit of normal value；Participants whose serum creatinine exceed the upper limit of normal value；Participants who suffer from dysfunction of blood coagulation (thrombocytopenia, bleeder disease, etc.)
6. Participants who have systemic infection or infectious disease.
7. Participants who suffer from serious skin defect or ulcer around the studying knee joint.
8. Participants who suffer from typical varus or valgus deformities or lack of articular cavity.
9. Participants with diabetes and have to inject insulin or who are not good enough to control the blood glucose (FBG ( fasting blood-glucose) ≥10mmol/L.)
10. Participants who suffer from cancer (within 5 years) or Alzheimer's disease.
11. Participants with score 0 or 4 of the studying knee joint evaluated by radiological Kellgren-Lawrence grading scale.
12. Participants who have hormone drugs within 2 weeks or analgesic drugs within 1 week before this trial or take part in other clinical trials.
13. Participants whose studying knee receives articular cavity therapy within 3 months, containing intra articular administration, articular irrigation and arthroscopic surgery
14. Participants with an allergy to the experimental drugs.
15. Participants who are not suitable for this trial judged by the researchers.