The primary objective of this study is to assess the safety of a single injection of APS.

The primary objective of this study is to assess the safety of a single injection of APS in patients with painful unilateral knee osteoarthritis and who have not been able to get satisfactory pain relief with other treatments through one-month post treatment and monitor subjects for adverse events through 12 months.

Inclusion Criteria:

• Male or female ≥40 and ≤75 years old at time of injection..
• A standing radiograph of the knee showing a Kellgren-Lawrence grade of 2 to 4 (within 6 months of screening).
• Body mass index ≤40 kg/m2.
• A Western Ontario and McMaster Universities osteoarthritis index using the Likert scale, Version 3. (WOMAC LK 3.1) pain subscale total score ≥ 10 and ≤ 19.
• Has undergone at least two prior conservative OA therapies without satisfactory pain relief.
• Patient has failed to get satisfactory pain relief from either HA or steroid injections or would be considered an appropriate patient to receive either HA or steroid injections

Exclusion Criteria:

• Presence of active infection or abnormal effusion in the knee immediately preceding treatment injection.
• Presence of symptomatic OA in the non-study knee
• Diagnosed with rheumatoid arthritis, Reiter's syndrome, psoriatic arthritis, gout, ankylosing spondylitis, chondromalacia, arthritis secondary to other inflammatory diseases, or of metabolic origin; HIV, viral hepatitis; chondrocalcinosis, Paget's disease, villonodular synovitis, and other non-OA joint disease.
• Disease of spine, hip or other lower extremity joints of sufficient degree to affect assessment of the index knee
• Untreated symptomatic injury of index knee (e.g., acute traumatic injury, anterior cruciate ligament injury, meniscus injury, cartilage lesion).
• Knee radiographs showing bone-on-bone or other gross cartilage deficits.
• Presence of surgical hardware or other foreign body in the index knee.
• Intra-articular steroid injections in the index knee within 3 months of screening.
• Intra-articular HA in the index knee within 6 months of screening.
• Other intra-articular therapy in the index knee within 6 months prior to screening.
• Systemic steroid use within 2 weeks of screening.
• Planned/anticipated surgery of the index knee during the study period.
• A history of local anesthetic allergy
• Use of systemic immunosuppressants within six weeks of treatment.
• Currently on anticoagulant therapy
• Any documented clinically significant condition (e.g., diabetes, malignancy), finding, or psychiatric illness at screening which could compromise patient safety or interfere with the assessment of the safety and treatment effects of the study injection.
• Skin breakdown at the index knee where the injection is planned to take place.
• Pregnant or nursing mothers or women who are planning on getting pregnant during the time they will be participating in the study.
• Known drug or alcohol dependence currently or within the last year.
• Used any investigational drug or device within 30 days prior to screening.
• Used any investigational biologic within 60 days prior to screening

The included population could generally be characterized as patients with painful unilateral knee OA, who had not been able to get satisfactory pain relief with other treatments.