This phase I and II double blinded randomized clinical controlled trial investigates the safety and efficacy of intraarticular knee injection with allogenic adipose derived mesenchymal stem cells (AD-MSC), in patients suffering from mild-moderate knee osteoarthritis compared to placebo injection with saline.

Inclusion Criteria:

• Chronic knee pain (defined for at least 6 months with NRS 4 or above when pain worst)
• Patients with Grade II-III osteoarthritis according to the Kellgren Lawrence Classification and a joint width space of 1-3 mm.
• Axial hip, knee, ankle x-ray with no more than 5 degrees valgus/varus deformity
• Medial, lateral or dual compartment OA as determined above
• BMI <35
• Danish speaker
• Patients must be legally competent and must be able to sign the written consent

Exclusion Criteria:

• Severe Osteoarthritis (Grade IV according to Kellgren Lavrence Classification)
• Intraarticular tumor, infection or fracture
• Pregnancy and breast feeding
• Cognitive impairment
• Treatment with cytostatic drugs
• Previous intraarticular knee injection in the past 3 mo.
• Unable to perform MRI scan (non-compatible implants, claustrophobia and severe obesity(>BMI 35)
• Previous ligament reconstruction
• Meniscal operation with resection with more than 50% or multiple meniscal operations (more than one resection)
• Diabetes mellitus type 1 and 2
• Knee instability on physical examination
• History of allergy to antibiotics
• Concomitant severe infection, malignant tumor, coagulation diseases or uncontrolled or unmanaged systemic disease
• Presence of other types of inflammatory arthritis

Double-blinded (participant and investigator)