The purpose of this study is to demonstrate non-inferiority of three weekly intra-articular injections of SUPARTZ to three weekly intra-articular injections of Euflexxa for the relief of knee OA.

The purpose of this study is to demonstrate non-inferiority of three weekly intra-articular injections of SUPARTZ to three weekly intra-articular injections of Euflexxa for the relief of knee joint pain in subjects with osteoarthritis (OA) of the knee as measured by the VAS (0-100 mm) Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain subscale score Change from Baseline (CFB) over Weeks 3, 6, 12.

Safety will be accessed by recording adverse events, concomitant medications, physical examinations, and vital signs.

Inclusion Criteria:

• Clinical evidence of symptomatic osteoarthritis of the study knee as classified according to Altman criteria.
• Symptoms in study knee for at least one year prior to the screening visit
• Verified OA of the study knee of Grade 2 or 3 according to a modification of the grading system of Kellgren-Lawrence (K-L) radiographic severity.
• Willingness to discontinue NSAIDs (systemic and topical) and non-acetaminophen analgesic use seven days or five half-lives prior to the first injection and throughout the study.

Exclusion Criteria:

• Inability to perform a 50 foot walk test.
• Subjects with rheumatoid arthritis, joint infection, other inflammatory and metabolic arthritis, Lupus or dermatologic disorder or skin conditions in close proximity to study knee that would preclude safe intra-articular injections.
• Prior hyaluronic acid injections into the study knee within six months of the screening visit.
• Intra-articular or intra-muscular steroid injections within three months of the screening visit or during study participation. Oral corticosteroids within four weeks of the screening visit or during study participation.
• History of surgical treatment to the study knee or arthroscopic intervention within three months prior to the screening visit.
• Clinically apparent tense effusion of the study knee on examination determined by either a positive bulge sign or positive ballottement of the patella (patellar tap).
• Subjects with clinically diagnosed symptomatic OA of the hip.

All but 1 subject who discontinued after being randomized to Euflexxa but unable to tolerate the injection procedure. This subject did not receive any of the study device via injection.

26 Weeks (12 week primary period plus 14 week extension phase)