The purpose of this study to investigate the effect of using losartan (a blood pressure lowering drug with anti-scarring properties) on preventing primary postoperative arthrofibrosis (formation of abnormal scar tissue) in the knees in participants undergoing anterior cruciate ligament (ACL) repair surgery of their knee.

Losartan, an angiotensin-II receptor blocker (ARB), approved by the Food and Drug Administration (FDA) for the treatment of hypertension and diabetic nephropathy, has garnered recent interest in the field of orthopedic surgery as an anti-fibrotic (anti-scarring) agent. Losartan's primary mechanism of action as an anti-hypertensive involves acting as a receptor antagonist for angiotensin II, a peptide produced by the liver which causes vasoconstriction, release of anti-diuretic hormone from the pituitary gland, and release of aldosterone from the adrenal glands, among other functions. Losartan secondary function is to act as a TGF-β1 blocker. TGF-β1 has been implicated in pro-fibrotic pathways in multiple organs systems. Losartan, initially as a treatment for hypertension and diabetic nephropathy, was found to have benefits against fibrosis in the renal system. As a result, the use of losartan has gained interest in several other fields in medicine, including plastic surgery for wound healing and keloid prevention, in ophthalmology to prevent corneal scarring, and orthopedic surgery. The potential use of losartan presents an attractive anti-fibrotic prophylaxis candidate against the formation of postoperative arthrofibrosis following ACLR.

Inclusion Criteria:

• Must be undergoing a primary ACLR with or without the following:
• Chondroplasty
• Synovectomy
• Loose body removal
• Removal of hardware
• Meniscal surgery (excluding meniscal allograft transplantation/MAT)
• Lateral extra-articular tenodesis
• Must have skeletal maturity in the distal femur and proximal tibial physes
• Must be age 18 years or older at time of enrollment

Exclusion Criteria:

• <18 years at time of enrollment
• No diagnosis of ACL tear
• ACL repairs
• Revision ACL reconstructions
• Open distal femur or proximal tibia physes
• Major concomitant procedures (such as osteotomy, MAT, or cartilage restoration surgery)
• History of prior proximal or distal femur fracture (including those receiving nonoperative treatment)
• History of prior ipsilateral femur or tibia osteomyelitis
• Medical history
• History of hypotensive disease, including postural orthostatic hypotension syndrome (POTS), autonomic dysreflexia, or Shy-Drager syndrome (aka multiple system atrophy), baseline hypotension <90 systolic or <60 diastolic mmHg.
• History of significant hepatic disease (liver transplantation, cirrhosis of any cause, or any liver disease with Child-Pugh classification B or C) due to hepatic metabolism of ARBs.
• Chronic kidney disease
• Rheumatologic disorders on immunologic medications
• Current medications including diuretics (i.e. furosemide), lithium, and spironolactone
• Current hypertension with prescription of an ARB or ACE-I
• Allergy to losartan
• Current pregnancy or breastfeeding