The goal of this study is to demonstrate the clinical improvement and safety in patients treated with MONOVISC for ankle osteoarthritis. Specifically, this study will provide confirmation to the effectiveness and safety of MONOVISC at relieving ankle joint pain to 6 months post-treatment.

Obtain real world, post market data to confirm the clinical improvement and safety in patients treated with a single injection of MONOVISC for the symptomatic relief of osteoarthritis in the ankle joint. The entire study duration from first subject in to last subject out will be approximately one and half years. The enrollment phase will be approximately 12 months with a follow-up phase of 6 months. Visits will be scheduled at screening, baseline, 1 month, 3 months and 6 months post treatment.

Inclusion Criteria:

1. Age 18 years or older
2. Body Mass Index (BMI) ≤ 35 kg/m2
3. Diagnosis of symptomatic osteoarthritic joint in the index joint (Kellgren-Lawrence grade I to III) to be treated with MONOVISC injection.
4. Failed conservative treatment for joint osteoarthritis.
5. NRS pain on walking ≥4 and ≤9 in the index joint.
6. Subject must be willing to abstain from other treatments of the index joint for the duration of the study.
7. Subject is willing to discontinue all analgesics including NSAIDs, except acetaminophen/paracetamol, at least seven days before the treatment injection and through the completion of the study.
8. Subject is willing to use only acetaminophen/paracetamol (up to a maximum of 4.0 grams per day per the package insert) for the treatment of joint pain for the duration of the study. At least forty-eight hours prior to the Baseline Visit and each follow-up visit, the subject is willing to discontinue use of acetaminophen/paracetamol.
9. Subject is willing to maintain a stable dose of oral glucosamine and/or chondroitin sulfate products throughout the study, if taken prior to signing the informed consent form (ICF).
10. Able and willing to provide signed informed consent.

Exclusion Criteria:

1. History of hypersensitivity to any of the ingredients in the hyaluronan
2. Infection or skin disease in the area of the injection site or index joint
3. NRS pain on walking > 3 in the contralateral joint
4. NRS pain on walking > 3 in the ipsilateral knee or hip
5. Subject received an injection of Hyaluronic Acid (HA) and/or steroid in either joint within 6 months of signing the informed consent form (ICF). A subject will be excluded if they are planning to receive an HA or steroid injection (other than the study injection) in either joint during the course of this study.
6. Known inflammatory or autoimmune disorders (including rheumatoid arthritis, gout), or other pre-existing medical conditions that, in the opinion of the investigator, could impact treatment of the index joint or affect the ability of the subject to accurately complete the study questionnaires and comply with the study requirements.
7. Subject is taking medications at the time of signing the ICF which could interfere with the treatment procedure, healing and/or assessments. This includes but is not limited to oral or injectable anticoagulant treatments, anti-aggregant platelet treatment, chronic opioid analgesics. Low dose aspirin used for cardiovascular protection is allowed if a stable regimen is maintained for the duration of the study.
8. Subjects who had an oral, intramuscular, intravenous, rectal suppository or topical (excluded in index joint only) corticosteroid prior 30 days of signing the ICF are excluded. Topical corticosteroid use at any site other than the index joint is allowed.
9. Significant trauma to the index ankle within 26 weeks of screening
10. Chronic use of narcotics or cannabis.
11. Ligament instability or tear in index joint.
12. Chronic impingement in the index joint requiring surgical treatment
13. Diagnosis of fibromyalgia
14. Diagnosis of osteonecrosis in index joint
15. Subject has significant varus or valgus deformity greater than 10 degrees in either knee.
16. Subject requires consistent use of an assistive device (e.g. wheelchair, walker, etc.) Occasional use of a cane is acceptable.
17. Uncontrolled diabetes with HbA1c of >7%.
18. Subject is a woman who is pregnant or breastfeeding at the Screening Visit or a woman of child bearing potential who refuses to use effective contraception during the course of the study.
19. Subject is receiving or in litigation for worker's compensation.
20. Otherwise determined by the investigator to be medically unsuitable for participation in this study.

Single injection of MONOVISC into the Index Ankle

Adverse Events were collected from the time of the Baseline Study Visit until Study Completion at 26 Weeks (6 Months).

The definitions of adverse events and serious adverse events is the same as used in the clinicaltrials.gov definitions.

The incidence, timing, severity, and relationship to treatment of all Adverse Events (AE) were collected and coded using Medical Dictionary for Regulatory Activities (MedDRA).

There were no limitations or caveats associated with the conduct of this trial.