This is a multi-center, randomized, double-blind clinical investigation to compare the effectiveness of intra-articular polyacrylamide hydrogel (PAAG-OA) and a hyaluronic acid, Synvisc-One to induce symptomatic benefit in subjects with knee osteoarthritis.

The trial is designed as a multi-center, randomised, controlled, double-blind, and parallel-group trial spanning over 12 months with outcome assessments at baseline, 1, 3, 6 and 12 months incl. follow-up period between 2-5 years. Primary endpoint at 6 months. The trial is designed to compare effectiveness and safety of injection of PAAG-OA and Synvisc-One® in participants with knee OA.

Inclusion Criteria:

• Signed and dated informed consent form
• Stated willingness to comply with all study procedures and availability for the duration of the study
• Male or female, aged ≥ 40 years
• Clinical diagnosis of knee OA American College of Rheumatology criteria confirmed by radiology
• Definite radiographic OA in the most symptomatic knee (target knee) at mild to moderate-stage (Kellgren-Lawrence grades 2 or 3)
• Stable dose of analgesics for the past four weeks
• NRS (11 points (0-10) pain intensity numerical rating scale) ≥ 4 in target knee, during the past week when walking
• Body Mass Index (BMI) between 20-35
• For females of reproductive potential: use of adequate contraception must be used throughout the trial

Exclusion Criteria:

• Female participants who are pregnant, lactating or planning pregnancy during the course of the clinical investigation
• Contraindications to PAAG-OA or Synvisc-One®, according to IB or Instruction for Use (IFU)
• Previous intra-articular injection of polyacrylamide gel in the target knee
• Previous intra-articular injection with hyaluronic acid or derivatives in target knee in the previous 6 months
• Significant valgus/varus deformity of the knee, ligamentous laxity or meniscal instability
• Other diseases in target knee than osteoarthritis
• Intra-articular injection of any substance other than hyaluronic acid (e.g. corticosteroids) in the target knee within the last 3 months
• Acute serious infection of any region that required hospital care or intravenous antibiotic treatment within the last 30 days, or oral antibiotic treatment within the last 14 days
• Skin disease or infections in the area of the injection site
• Infected or severely inflamed knees
• History of sepsis in any joint or any clinical concern for a subacute infectious process in the target knee
• History of surgery in the target knee within the past 6 months
• Symptomatic osteoarthritis of the hips, spine or ankle, that interferes with the evaluation of the target knee
• Planned surgery on any lower extremity
• Clinically significant venous or lymphatic stasis present in the legs
• Clinically apparent tense effusion or inflammation in the target knee
• Suffering from any unstable or severe cardio-vascular disease
• Any contraindication to intra-articular e.g. anticoagulant therapy or clinical concern for potential coagulopathy (e.g. liver disease)
• Any foreign material in the target joint
• Any significant medical condition (e.g. significant psychiatric or neurological disorders or active alcohol/drug abuse), any medical condition that is unstable/poorly controlled or other factors that may interfere with study participation
• Treatment with systemic steroids
• History of drug/alcohol abuse, mental dysfunction of other factors limiting their ability to cooperate fully
• Change in physiotherapy within the previous month
• Fibromyalgia
• Inflammatory or other disease/condition which may affect joints (e.g. rheumatoid arthritis, psoriatic arthritis and ankylosing spondylitis among others)
• Haemophilia
• Any other condition that in the opinion of the investigator put a potential participant at risk or otherwise precludes participation in the trial
• Known allergic reactions to components of Synvisc-One (avian protein)
• Known allergic reactions to antibiotics (azithromycin and moxifloxacin) or local anaesthesia
• Participation in any experimental device study within 6 months prior to enrolment, or participation in an experimental drug study within 1 month prior to enrolment

The subject and study staff will not know the treatment received. Only the unblinded injector will know the treatment.