ZILRETTA is the first and only approved treatment for osteoarthritis (OA) knee pain utilizing extended-release microsphere technology.

A non-opioid option for significant extended relief of OA knee pain

ZILRETTA microsphere


ZILRETTA employs proprietary microsphere technology combining triamcinolone acetonide — a commonly administered, immediate-release corticosteroid — with a polylactic-co-glycolic acid (PLGA) matrix to provide extended pain relief. ZILRETTA microspheres localize in synovial tissue at a primary source of OA knee pain and inflammation. ZILRETTA has treated over 250,000 patients.1*

The pivotal Phase 3 trial, on which the approval of ZILRETTA was based, showed that ZILRETTA significantly reduced OA knee pain for 12 weeks, with some people experiencing pain relief through Week 16. ZILRETTA received approval from the U.S. Food and Drug Administration on October 6, 2017.


In a Phase 3 trial, ZILRETTA provided significant improvement in average daily pain (ADP) intensity scores vs saline control at Month 3 (P<0.0001).2 Reductions in ADP extended to Month 4.


4 days median time to onset with
ZILRETTA vs 11 days for saline control.3

>50% of patients experienced no or mild knee pain as early as Week 1 (1%/50%, respectively)1,4


~70% of patients experience no/mild knee
pain from Month 1 to Month 3.1,4

>50% of patients Percentage of 161 ZILRETTA-treatment patients experiencing no or mild knee pain at Month 1(21%/49%), and Month 4 (15%/44%), respectively


ZILRETTA microspheres localize in synovial
tissue, attaching directly at one of the primary
sources of OA knee pain and inflammation.5,6

In a pharmacokinetic study, intraariticular administration of ZILRETTA resulted in 18x lower peak plasma concentration compared with TA during the initial 24 hours following injection5


Clinical Trial Experience

The most common adverse events (incidence for ZILRETTA arm ≥1% and higher than saline control) in patients receiving a single injection in pooled clinical studies were sinusitis, cough, and contusions.

Phase 3 study: ZILRETTA was studied in a multicenter, international, randomized, double-blind, parallel-arm, placebo (saline)- and active-controlled (TAcs) trial that evaluated patients with moderate to severe OA knee pain (N=484). The primary endpoint was defined as change from baseline at Month 3 in weekly mean ADP intensity scores vs saline control (P<0.0001). The secondary endpoint are under the effect curve (AUE) baseline to Month 3 in weekly mean ADP scores with ZILRETTA vs TAcs was not met. Exploratory endpoints included time to onset of pain relief and change from baseline to each week in weekly mean ADP scores.

*Real-world use as of September 2020.

Defined as time from IA injection to the first daily pain assessment of >30% improvement from baseline

Stay informed about ZILRETTA.



ZILRETTA® (triamcinolone acetonide extended-release injectable suspension) is indicated as an intra-articular injection for the management of osteoarthritis pain of the knee.

Limitation of Use: The efficacy and safety of repeat administration of ZILRETTA have not been demonstrated.


ZILRETTA is contraindicated in patients who are hypersensitive to triamcinolone acetonide, corticosteroids, or any components of the product.

Warnings and Precautions

  • Intra-articular Use Only: ZILRETTA has not been evaluated and should not be administered by epidural, intrathecal, intravenous, intraocular, intramuscular, intradermal, or subcutaneous routes. Serious events have been reported with epidural and intrathecal administration of corticosteroids and none are approved for this use. ZILRETTA should not be considered safe for epidural or intrathecal administration.
  • Hypersensitivity Reactions: Rare instances of anaphylaxis, including serious cases, have occurred in patients with hypersensitivity to corticosteroids.
  • Joint Infection and Damage: A marked increase in pain accompanied by local swelling, restriction of joint motion, fever, and malaise are suggestive of septic arthritis. Examine joint fluid to exclude a septic process. If diagnosis is confirmed, institute appropriate antimicrobial therapy. Avoid injecting corticosteroids into a previously infected or unstable joint. Intra-articular administration may result in damage to joint tissues.
  • Increased Risk of Infections: Infection with any pathogen in any location of the body may be associated with corticosteroid use. Corticosteroids may increase the susceptibility to new infection and decrease resistance and the ability to localize infection.
  • Alterations in Endocrine Function: Corticosteroids can produce reversible hypothalamic-pituitary-adrenal axis suppression, with potential for adrenal insufficiency after withdrawal of treatment, which may persist for months. In situations of stress during that period, institute corticosteroid replacement therapy.
  • Cardiovascular and Renal Effects: Corticosteroids can cause blood pressure elevation, salt and water retention, and increased potassium excretion. Monitor patients with congestive heart failure, hypertension, and renal insufficiency for edema, weight gain, and electrolyte imbalance. Dietary salt restriction and potassium supplementation may be needed.
  • Increased Intraocular Pressure: Corticosteroid use may be associated with increased intraocular pressure. Monitor patients with elevated intraocular pressure for potential treatment adjustment.
  • Gastrointestinal Perforation: Corticosteroid administration may increase risk of gastrointestinal perforation in patients with certain GI disorders and fresh intestinal anastomoses. Avoid corticosteroids in these patients.
  • Alterations in Bone Density: Corticosteroids decrease bone formation and increase bone resorption. Special consideration should be given to patients with or at increased risk of osteoporosis prior to treatment.
  • Behavior and Mood Disturbances: Corticosteroids may cause adverse psychiatric reactions. Prior to treatment, special consideration should be given to patients with previous or current emotional instability or psychiatric illness. Advise patients to immediately report any behavior or mood disturbances.

Adverse Reactions

The most commonly reported adverse reactions (incidence ≥1%) in clinical studies included sinusitis, cough, and contusions.

Please see full Prescribing Information.


  1. Data on file. Flexion Therapeutics, Inc.
  2. Conaghan PG, Hunter DJ, Cohen SB, et al. Effects of a single intra-articular injection of a microsphere formulation of triamcinolone acetonide on knee osteoarthritis pain: a double-blinded, randomized, placebo-controlled, multinational study. J Bone Joint Surg Am. 2018;100(8):666- 677.
  3. Study of FX006 for the treatment of pain in patients with osteoarthritis of the knee. ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT02357459 Published February 6, 2016. Updated February 7, 2018. Accessed April 26, 2021.
  4. Kapstad H, Hanestad BR, Langeland N, Rustøen T, Stavem K. Cutpoints for mild, moderate and severe pain in patients with osteoarthritis of the hip or knee ready for joint replacement surgery. BMC Musculoskelet Disord. 2008;9:55.
  5. Kraus VB, Conaghan PG, Aazami HA, et al. Synovial and systemic pharmacokinetics (PK) of triamcinolone acetonide (TA) following intra-articular (IA) injection of an extended-release microsphere-based formulation (FX006) or standard crystalline suspension in patients with knee osteoarthritis (OA). Osteoarthritis Cartilage. 2018;26(1):34-42.
  6. Bodick N, Williamson T, Strand V, et al. Local effects following single and repeat intra-articular injections of triamcinolone acetonide extended-release: results from three nonclinical toxicity studies in dogs. Rheumatol Ther. 2018;5(2):475-498