Human Umbilical Cord Mesenchymal Stem Cells in the Treatment of Knee Osteoarthritis

Inclusion Criteria: * Patients who have no major organ dysfunction. * Diagnosed as moderate to severe knee osteoarthritis according to internationally recognized criteria: a). Meets the criteria of the "Guidelines for the Diagnosis and Treatment of Osteoarthritis (2018 Edition)" revised by the Chinese Medical Association Rheumatology Branch in 2018; b). Meets the criteria of Grade 3 or more according to the American College of Rheumatology (ACR); c).Meets the criteria of Grade Ⅲ or more according to Kellgren-Lawrence's OA radiology grading standard. * Those who have the ability to move independently, except those who use wheelchairs, walkers or crutches, and who have no history of mental illness. * There is no obvious contraindication to articular cavity injection in hematology and biochemical testing. * No local or systemic infection. * Subjects and their families understand the clinical trial protocol and agree to participate in the trial, and sign a written Informed Consent. * Patients whose pain has lasted for more than half a year, and the routine clinical treatment of oral hormones, opioids and other drugs have been ineffective. Exclusion Criteria: * Those who are older than 70 years old or younger than 18 years old, or have no full capacity for civil conduct. * HIV, hepatitis virus or syphilis virus infection or positive serological test. * Body mass index (BMI) greater than 30 kg/m2. * Congenital or acquired knee deformity; severe knee arthritis accompanied by severe varus deformity, with varus greater than 10°. * Pregnant or lactating women, or women of childbearing age who have a positive pregnancy test within 7 days before receiving treatment. * Complicated with severe cardiovascular and cerebrovascular, liver, kidney, and endocrine, blood system diseases, malignant tumors, allergies, mental disorders, acute infections or local knee joint infections. * Patients with immunodeficiency. * Patients with a history of intra-articular injection within 3 months; patients being treated with immunosuppressive agents and glucocorticoids. * Patients who are still participating in other clinical trials. * Subjects who refuse to sign Informed Consent or refuse to participate in this clinical trial.