The purpose of this study is to evaluate the efficacy of Losartan use post-operatively for reducing or preventing the development of arthrofibrosis and the associated adverse impacts on clinical outcomes.

This is a double-blind, randomized, placebo-controlled clinical trial proposed to evaluate the efficacy and safety of Losartan for reducing or preventing arthrofibrosis and improving patient-reported outcomes after total knee arthroplasty (TKA). Fibrosis will be evaluated over time after TKA using measures of knee range of motion and capsular thickening.

120 patients scheduled to undergo total knee arthroplasty will be recruited from the clinical practice of the Principal Clinical Investigator or his designee at The Steadman Clinic (TSC) and randomized into one of two arms (1:1).

Inclusion Criteria:

1. Planned primary total knee arthroplasty of a single knee;
2. Male or female ≥ 18 years of age;
3. Capacity to personally give informed consent (consent via legally authorized representative will not be accepted) and who are willing to comply with all study-related procedures and assessments.

Exclusion Criteria:

1. Breastfeeding, pregnant, or planning to become pregnant during participation in the study;
2. Diagnosed with inflammatory or other arthritis caused by autoimmune disease affecting the study knee;
3. Previous knee arthroplasty on the study knee;
4. Previous infection affecting the study knee;
5. Planned total knee arthroplasty of contralateral knee to occur at any point during the study participation period;
6. Are hypotensive as confirmed by Principal Clinical Investigator or appropriate designee;
7. Planned lower extremity surgery (other than TKA in the study leg) for the duration of study participation;
8. Any condition other than knee osteoarthritis that significantly impairs ability to walk or perform other activities of daily living;
9. Currently taking: Losartan or other medication in the same drug class; Warfarin or related anticoagulants;
10. Opioid analgesics taken in the past 8 weeks and are not willing to discontinue these medications through the duration of the study (except as prescribed as standard of care in the immediate post-operative period);
11. Allergic to any active or inactive ingredient of Losartan;
12. Taking medication with known adverse Losartan interaction;
13. Subjects that have any medical condition, including malignancies, laboratory findings, and/or findings in the medical history or in the pre-study assessments that, in the opinion of the Investigator, constitutes a risk or contraindication for participation in the study or that could interfere with the study objectives, conduct, or evaluation, or prevent the patient from fully participating in all aspects of the study.

The Investigator or properly trained and delegated study team member (Physician Assistant) will write the prescription for the study medication. The subject's randomization number will be communicated directly to the Vail Health pharmacy. The Vail Health pharmacy will maintain an unblinded, de-identified randomization spreadsheet that documents group allocation for each subject. The Vail Health Pharmacy oversees and manages drug disbursement for research.