Synovitis has an important role in the symptoms and progression of Osteoarthritis (OA). Inflamed synovium has been associated with both increased symptoms and increased progression in OA patients. Furthermore, synovitis observed during knee arthroscopy in our patients undergoing arthroscopic partial meniscectomy (APM) was associated with worse symptoms while adjusting for confounding factors.Therefore, a better understanding of synovitis as a predictor of outcome after APM and as a target for treatment is needed to improve outcomes in this patient population.

Triamcinolone has been shown to decrease synovitis-associated outcomes in both animal and human studies after anterior cruciate ligament (ACL) injury. In a porcine model of ACL injury, treatment with triamcinolone resulted in decreased formation of synovitis-related collagen breakdown products as well as decreased cellularity of the synovium.And in a trial of triamcinolone injected after ACL injury, similar findings of decreased C-telopeptide of type II collagen (CTX-II), associated with collagen type II breakdown, was found in knees administered triamcinolone compared to placebo controls.

Symptomatic meniscal tear with pain and mechanical symptoms of catching and locking ,a phenotype of early OA, and often prompts patients who have failed physical therapy to elect APM to improve their symptoms. This arthroscopic surgery presents a unique opportunity to evaluate the intraarticular status of the joint including joint fluid biomarkers and synovial tissue for signs of inflammation in patients with mild to moderate OA. Since no post-op tissue repair is desired after APM, in contrast to other post-traumatic OA (PTOA) models such as anterior cruciate ligament reconstruction, the APM cohort can be used to test novel interventions to slow down PTOA development by suppressing synovitis and inflammation. Results from this trial in this patient population could be applied to the broader population of many millions of patients with mild to moderate OA who never undergo arthroscopy.

There are currently approximately 1,000,000 APMs performed in the United States each year, and about 70 percent of patients have a clinically significant improvement in symptoms after surgery. Much of this variation in outcome is unexplained but is hypothesized to be related to synovitis and joint inflammation that is currently unmeasured and untreated in usual clinical care.

This is a randomized controlled trial of extended release triamcinolone for efficacy to improve patient reported outcome measures after APM. The investigators will evaluate joint fluid and synovial tissue biomarkers to assess joint inflammation as a predictor of treatment response, use quantitative 3T MRI to evaluate cartilage and meniscus composition and 3D bone shape, which are sensitive imaging markers for early joint degeneration, and use a prospective surgical episode data collection system to capture patient reported outcomes and surgeon reported operative data.

Inclusion Criteria:

1. Male or female age 40 and older
2. Scheduled for APM with enrolling surgeon
3. Arthroscopic evidence of structural OA including at least one surface with grade 2 chondral change
4. Written informed consent (and assent when applicable) obtained from subject or subject's legal representative and ability for subject to comply with the requirements of the study.

Exclusion Criteria:

1. Females who are pregnant or nursing or plan to become pregnant during the study; men who plan to inseminate a partner or donate sperm
2. Presence of a condition or abnormality that in the opinion of the Investigator would compromise the safety of the patient or the quality of the data.
3. Known or suspected hypersensitivity to Zilretta (or component of Zilretta) or triamcinolone acetonide
4. Kellgren and Lawrence Grade IV (severe OA; arthroplasty is typically preferred over APM in this setting)
5. Injection with corticosteroid into affected knee in past 12 weeks
6. Injection with platelet rich plasma into affected knee in past 12 weeks
7. Injection with hyaluronic acid into affected knee in past 24 weeks
8. Plan for cartilage resurfacing procedure (microfracture, autologous chondrocyte implantation, osteochondral autograft or allograft), ligament reconstruction or other open procedure
9. Bilateral surgery
10. Unable to undergo MRI due to implanted medical device, aneurysm clamp, metal fragments in eye, etc.
11. Absence of at least one area of grade 2 chondral change on diagnostic arthroscopy (patients without structural OA are excluded)