Inclusion Criteria:  Patients who are ≥ 19 years of age on the date on which the consent form was signed Patients diagnosed with knee osteoarthritis in at least one knee according to the clinical and radiological definition criteria of American College of Rheumatology (ACR) guidline at screening visit Patients with knee OA corresponding to K&L Grade 2 or 3 on radiographic examination at screening visit Patients with less than 35 of BMI at screening visit Patients who voluntarily decide to participate and sign the consent form Patients who have persistent symptoms despite having undergone a reasonable trial of standard therapy (i.e., for a minimum of 3 months)  Exclusion Criteria:  Patients with any of the following diseases.  - infectious arthritis, autoimmune or inflammatory joint diseases, gout, recurrent pseudogout, Paget's disease, intra-articular displaced fracture, ochronosis, acromegaly, haemochromatosis, Wilson's disease, genetic disease (hyperkinesia etc.), genetic collagen disorder, etc.  Patients who have ever undergone surgery or radiotherapy in the knee joint area within the 12 weeks prior to the screening visit date, or who have not been recovered from its side effect yet. Patients with SIF (Subchondral insufficiency fracture) corresponding to type II of the RPOA (rapidly progressive osteoarthritis). Patients whose physical examination results show severe degree of ligament instability. Patients who have ever been given any intraarticular drug injection (i.e., hyaluronic acid injection, etc.) in to-be-treated (index) knee within the 6 months, prior to the screening visit date. Patients who have ever been given steroids via intraarticular injection in to-be-treated (index) knee within the 12 weeks prior to the screening visit date.  Patients who have ever taken medications or given therapy below within the past 2 weeks on the basis of screening visit date. However, if patients have 14 days of wash-out period, the patient is allowed to participate.  drugs containing the ingredient of glucosamine, chondroitin sulfate, or diacerein drugs containing herbal ingredient or herbal drugs for knee OA pain relief anti-inflammatory analgesics or NSAIDs (prescription/non-prescription drugs). (However, patients who take acetaminophen and have 3 days of wash-out period are allowed to participate.) oral steroids hospital physiotherpy or oriental medicine treatment (buhang, acupunture, moxibustion etc.) Patients who have skin disease on injection site or who are judged inappropriate for intra-articular injection on to-be-treated knee. Patients who are judged unsuitable for MRI scanning (3.0 Tesla or higher) due to an insertion of metal material (i.e., heart pacemaker, cerebral aneurysm clip, etc.) or obstructive phobia. However, patients who have an insertion of metal material that is not affected by the magnetic field is allowed to participate  Patients with clinically significant past or present illness as follows;  heart diseases (i.e., myocardial infarction, coronary artery bypass surgery, arrhythmia and other serious heart diseases, etc.) uncontrolled hypertension (not controlled down to 140/90 mmHg or below even after treatment with 3 or more antihypertensive drugs) kidney disease (i.e., chronic kidney failure, glomerulonephritis, etc.) liver disease (i.e., acute or chronic liver disease such as cirrhosis, fatty liver, etc.) endocrine diseases (i.e., thyroiditis, diabetes insipidus, Cushing's disease, etc.) other serious systemic diseases Patient with ongoing autoimmune disorder that requires treatment with an immunosuppressive medication Patients with infection that requires administration of parenteral antibiotics Patients with a history of mental illness or epilepsy Patients who have been diagnosed with cancer within the 5 years prior to the screening visit date Patients who have been given immunosuppressive drugs such as cyclosporin A or azathioprine within the 6 weeks prior to the screening visit Patients with a history of allergic reactions to hyaluronic acid injections, cryoprotectant (dimethyl sulfoxide, DMSO), or gentamicin. Patients who are pregnant or lactating, or patients who have a plan to become pregnant during the study period Male or female patients who do not agree to avoid pregnancy or the use of appropriate contraceptive methods during the study period. But women who have given infertility surgery or who have passed menopause one year or more are allowed to participate without the consent for contraception. Patients who have been given any other cell therapy products or who plan to do so during the study period. Patients who have been given any other investigational products including device within the 3 months prior to the screening visit date. Patients who are judged by the investigator as inappropriate for enrollment into the study, for any reasons other than the reasons specified above.