Effect of Zilretta Injection

The purpose of this study is to examine the pre-post effects of a single ZILRETTA knee injection on physiological measures of self-reported pain and disability, physical performance, and physical activity in individuals with knee osteoarthritis (OA). The investigators will recruit 35 symptomatic knee OA patients for this study. All data will be collected prior to injection (baseline), as well as at 4 (post 1) and 8-week follow-ups (post 2).

Individuals with knee osteoarthritis (OA) demonstrate significant physical disability which leads to diminished physical activity, a lesser quality of life, as well as a higher risk of inactivity related comorbidities including mortality. This is thought to be caused by an inability to voluntarily activate your quadriceps muscle due, in part, to knee joint swelling and joint-related pain. Incomplete muscle activation causes quadriceps weakness.

Individuals with quadriceps weakness exhibit changes in their walking biomechanics which is associated with diminished physical function and lesser physical activity in those with knee OA. Therefore, it is critical to develop interventions that target mechanisms causing decreased quadriceps activation in order to restore optimal walking biomechanics and improve physical activity.

The ZILRETTA knee injection is an FDA approved, extended release corticosteroid for in patients with knee osteoarthritis and has been shown to reduced knee pain for 3 months in approximately 70% of patients. Currently, there are no studies that have examined ZILRETTA's objective effectiveness on physical activity, biomechanics, and performance tests in patients who have received an injection.

The overall purpose of the current study is to examine the effect of a ZILRETTA knee injection on functional and performance tests including quadriceps neuromuscular activation, quadriceps strength, walking gait biomechanics, and a battery of physical performance outcomes at 4 and 8-weeks following injection in 35 individuals with knee OA.

Eligibility Criteria:
Full Inclusion Criteria:

* Male or female between the ages of 40 and 75 years old who:
* Exhibit symptomatic knee OA, defined as a normalized WOMAC function subscale score \>31(out of 100 points, indicating highest degree of dysfunction)
* Have radiographic evidence of tibiofemoral OA (2-4 on the Kellgren-Lawrence scale)
* Provide written informed consent and the ability to comply with the requirements of the study.
* Be willing to abstain from use of the following protocol-restricted medications during the study:

  * Corticosteroid injections into the knee or any lower extremity joint will be restricted for 3 months prior to the screening visit (based on the drug half-life) and throughout the entirety of the study period including the 8-week follow-up test. Information about when the latest corticosteroid injection occurred for each participant prior to screening in order to determine when each participant can attend the screening visit.
  * Hyaluronic acid injections into the knee or any lower extremity joint will be restricted for 6 months prior to the screening visit (based on the drug half-life) and throughout the entirety of the study period including the 8-week follow-up test. Information about when the latest hyaluronic acid injection occurred for each participant prior to screening in order to determine when each participant can attend the screening visit.
  * Prescription Depressants (Examples: opiates and opioids, barbiturates, tranquilizers and benzodiazepines) will be restricted 4-weeks prior to screening and throughout the study period as these medications may affect the neuromuscular function.
  * Prescription Stimulants (Example: amphetamines) will be restricted 4-weeks prior to screening and throughout the study period as these medications may affect the neuromuscular function
  * Non-steroidal anti-inflammatory drugs (NSAIDs) will be restricted 24 hours prior to screening or follow-up testing sessions. NSAID use will be tracked and patients instructed not to change their NSAIDs usage during the 8-weeks of the study.
  * Acetaminophen will be restricted 24 hours prior to screening or follow-up testing sessions. Acetaminophen use will be tracked and patients instructed not to change their Acetaminophen usage during the 8-weeks of the study.

Full Exclusion Criteria:

Potential participants meeting any of the following criteria (based on the electronic medical record or in laboratory screening) will be excluded if they:

* Are hypersensitive to triamcinolone acetonide, corticosteroids or any components of the product
* Have other intra-articular investigational drug/biologic use in the previous 6-months
* Have been diagnosed with a cardiovascular condition restricting exercise
* Have had a corticosteroid injection in the involved knee in the previous 3-months or hyaluronic acid injection in the involved knee in the previous 6-months
* Have a pacemaker
* Have a neurodegenerative condition
* Have rheumatoid arthritis
* Have diabetes
* Have cancer
* Have a neural sensory dysfunction over the knee
* Have a body mass index (BMI) over 35
* Have a history of lower extremity orthopaedic surgery in the past year
* Have a history of a traumatic knee injury in the past 6 months
* Have any history of total knee arthroplasty in either extremity
* Have a diagnosed, non-reconstructed knee ligament tear
* Need an assistive device to walk
* Are currently pregnant or planning to become pregnant while enrolled in the study
* Are taking medications that can react harmfully with injected corticosteroids

NOTE: Individuals that have bilateral knee OA will not be excluded unless they meet another exclusion criteria. In case a patient needs an injection in both knees, they will be excluded. Only one knee will be injected for this study.