This is an open-label study assessing the effect of the administration of a single intra-articular (IA) injection of FX006 32 mg on synovial volume in patients with osteoarthritis (OA) of the knee.

This is an open-label study assessing the effect of the administration of a single intra-articular (IA) injection of FX006 32 mg on synovial volume in patients with osteoarthritis (OA) of the knee. The study will be conducted in male and female patients who are ≥ 40 years of age.

Eligible patients who provide written consent and meet all entry criteria will undergo initial ultrasound examination and MRI with contrast of the index knee, and then receive a single IA injection of FX006 administered to the index knee at Baseline/Day 1. Patients will return to the clinic at Weeks 6 and 24 for an MRI with contrast of the index knee and other assessments. Patients must also have a blood sample drawn for Estimated Glomerular Filtration Rate (eGFR) testing within 30 days prior to the scheduled MRIs. In addition, a patient questionnaire will be administered and adverse events (AEs) and concomitant medication updates will be collected via telephone at Weeks 12 and 18.

Inclusion Criteria:

• Written consent to participate in the study
• Male or female ≥ 40 years of age
• Body mass index (BMI) ≤ 40 kg/m^2
• Ambulatory and in good general health
• Willing and able to comply with the study procedures and visit schedules and able to follow verbal and written instructions
• Willing to abstain from use of protocol-restricted medications during the study
• Symptoms associated with OA of the index knee for ≥ 6 months prior to Screening (patient self-report is acceptable)
• Currently meets American College of Rheumatology (ACR) Criteria (clinical and radiological) for OA
• Kellgren-Lawrence (K-L) Grade 2 or 3 in the index knee based on X-ray performed during Screening (centrally read)

Exclusion Criteria:

• Any inflammatory arthritis including reactive arthritis, rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, arthritis associated with inflammatory bowel disease, gout or secondary OA from gout
• History of infection or crystal disease in the index knee joint
• Unstable index knee joint (such as a torn anterior cruciate ligament) within 12 months of Screening
• Surgery or arthroscopy of the index knee within 12 months of Screening
• IA corticosteroid (investigational or marketed) in any joint within 3 months of Screening
• IA treatment of the index knee with hyaluronic acid (investigational or marketed) within 6 months of Screening
• IV or IM corticosteroids (investigational or marketed) within 3 months of Screening
• Oral corticosteroids (investigational or marketed) within 1 month of Screening
• Any other IA drug/biologic in the index knee within 6 months of Screening or 5 half-lives (whichever is longer) (e.g., platelet rich plasma (PRP) injection, stem cells, prolotherapy and amniotic fluid injection)
• Prior administration of FX006
• eGFR results <40 mL/minute
• Any contraindication to MRI Scanning (e.g., presence of certain ferromagnetic foreign bodies or electronic devices including most cardiac pacemakers, claustrophobia)
• Known hypersensitivity to any form of radiographic contrast
• Females who are pregnant or nursing or plan to become pregnant during the study; men who plan to conceive during the study