Losartan to Improve Outcomes after multi-ligament kNee injury (LION Trial)

Abstract

Background

Multi-ligament knee injuries (MLKI) are complex injury patterns that affect two or more ligaments of the knee. Although surgical intervention can improve functional and clinical outcomes, a large percentage of patients are unable to return to preoperative activity levels. One reason for this is loss of knee range of motion (ROM), which characterizes the exaggerated pro-inflammatory environment of arthrofibrosis and is associated with future osteoarthritis risk. The purpose of this study is to assess the effectiveness of a 30-day course of losartan, a common angiotensin II antagonist, in improving surgical outcomes one year after MLKI surgery by reducing arthrofibrosis and pro-inflammatory signaling. Our hypothesis is that individuals who undergo MLKI reconstruction and take losartan will report an increased ability to return to activity, improved ROM, and decreased synovitis.

Methods

This is a randomized, double-blinded, placebo-controlled clinical trial that aims to recruit 90 patients who are undergoing MLKI reconstruction. Upon enrollment, patients will be randomly assigned to a 30-day postoperative course of oral losartan or placebo on a 1:1 basis. The primary outcome will be the Cincinnati Occupational Rating Scale (CORS) Questionnaire Score which will quantify self-reported physical function. The secondary outcomes will include the time to return to active duty, work, and/or sport after surgery; International Knee Documentation Committee (IKDC) Subjective Knee Scores; Visual Analogue Scale (VAS) Pain Scores; knee ROM; quadricep strength; and ultrasound measures of persistent synovitis.

Discussion

There is an unmet need for interventions to reduce inflammation and arthrofibrosis following MLKI to both rescue ROM and improve rates of return to activity. The LION Trial is a randomized, placebo-controlled clinical trial that will evaluate the efficacy of a 30-day course of losartan following MLKI reconstruction. The results of this study have the potential to redefine perioperative management and improve long-term functional outcomes for all patients undergoing ligament reconstruction with a widely available and inexpensive medication.

Trial registration

Clinicaltrials.gov #NCT06933706. Registered on April 11th, 2025.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-026-09714-3.

Background

Whether the result of military training, a sports injury, or a traumatic event such as a motor vehicle accident, multi-ligament knee injuries (MLKI) can be devastating events. These complex injury patterns involve the disruption of two or more of the four major ligaments in the knee and often coincide with concomitant injuries to arteries, nerves, tendons, menisci, and bone that can permanently alter limb biomechanics [1]. Although surgical intervention has been shown to improve functional and clinical outcomes relative to nonsurgical treatment for MLKIs, 38% of patients nevertheless report postoperative complications [2, 3]. Loss of knee range of motion (ROM) is the most common complication after a MLKI and is significantly associated with military separation as it hinders the individual’s ability to perform both job-specific duties and standard fitness tests [4]. There are additional long-term ramifications of ROM loss, as the need for motion-restoring surgery after MLKI was a significant predictor of physician-diagnosed osteoarthritis within the next 5 years [5]. Considering these outcomes, an individual’s ability to perform daily tasks and higher demand physical activities is frequently impaired in both the short- and long-term, with only 46% of military personnel returning to active duty following an MLKI [6]. These detriments are similarly reflected in civilian populations, with only 39% of those experiencing MLKIs returning to work with little to no limitations and only between 22 and 33% of athletes recovering sufficiently to return to high-level competition [7].

The undesirable clinical outcomes of MLKIs can be understood through the lens of the molecular mechanisms of arthrofibrosis. Knee ligament injuries initiate a biochemical cascade contributing to pain, motion loss, and muscular changes [8–14]. In our analysis of the joint fluid proteome in the first 2 weeks following an anterior cruciate ligament (ACL) injury, fibronectin and extracellular matrix proteins associated with scar tissue formation were upregulated, setting the stage for arthrofibrosis [9]. Arthrofibrosis is a joint disorder characterized by excessive collagen production and adhesions mediated by pro-inflammatory cytokines and transforming growth factor-beta (TGF-β), which results in increased pain and decreased ROM [15–19]. TGF-β is therefore a key molecule in the development of postoperative pain and fibrosis, and it has been shown to be a significant predictor of arthrofibrosis after total knee arthroplasty (TKA) [19]. TGF-β also remained elevated for 4 weeks in approximately 30% of patients who underwent ACL reconstruction due to a lack of innate anti-inflammatory response, increasing risk of future arthrofibrosis [8].

There is an unmet need for interventions that mitigate the risk of motion loss and arthrofibrosis following MLKI reconstruction. Losartan is an FDA approved angiotensin II receptor blocker commonly used to treat hypertension [20]. However, because of its multiple mechanisms of action, low-cost, and widespread availability, it is a medication that could potentially be repurposed to reduce arthrofibrosis and improve outcomes following a MLKI. Mechanistically, losartan inhibits TGF-β signaling, which has been found to reduce pain, myofibroblast activity, synovitis, collagen deposition, fibrosis, and cartilage degeneration in multiple animal models [21–23]. Angiotensin II also contributes to inflammation and oxidative stress [24]. Therefore, by blocking the angiotensin II receptor, losartan has downstream anti-inflammatory effects that may further inhibit the progression of fibrosis [25–27]. Further, by modulating matrix metalloproteinase and tissue inhibitors of metalloproteinases, losartan may also mitigate fibrosis by promoting proper remodeling of the extracellular matrix [21, 28, 29]. In large clinical and health insurance databases, losartan use has been associated with a reduced incidence of motion-restoring surgery after TKA [30, 31]. Despite these promising results, to date no clinical translational studies have been performed to determine if early postoperative use of losartan may improve knee ROM, quadriceps muscle strength, or rates of persistent postoperative synovitis following a MLKI reconstruction.

Methods

Aims

The objective of this randomized clinical trial is to determine whether a 30-day postoperative course of oral losartan will improve a person’s ability to return to duty or sport, improve ROM, and lessen pain and inflammation after a MLKI. These endpoints will be evaluated using the CORS Score as the primary outcome variable, in addition to multiple secondary outcome variables (time to return to active duty, work, and/or sport after surgery; IKDC Subjective Knee Scores; VAS Pain Scores; knee ROM; quadriceps strength; and ultrasound measures of persistent synovitis). We hypothesize that by directly targeting the underlying mechanisms of postoperative pain and fibrosis, a 30-day course of oral losartan will improve a person’s ability to return to duty or sport, improve pain and ROM, and resolve persistent inflammation after a MLKI. Specifically, we will test the following aims:

AIM 1

Determine if a 30-day postoperative course of losartan improves the ability to return to duty or sports via patient-reported outcomes when compared to placebo following MLKI reconstruction.

Hypothesis

Compared to placebo, losartan will result in greater CORS Scores 12 months after surgery, as well as an earlier return to duty or sport and greater improvements in IKDC Subjective Knee Scores and pain scores at all post-treatment time points.

AIM 2

Assess whether losartan results in more symmetric knee ROM and quadriceps strength following MLKI reconstruction when compared to placebo.

Hypothesis

The losartan group will demonstrate improved ROM and quadricep strength after MLKI reconstruction at all post-treatment time points when compared to placebo.

AIM 3

Compare ultrasound measures of synovitis and effusion between groups treated with losartan versus placebo following MLKI reconstruction.

Hypothesis

Significantly fewer people in the losartan group will demonstrate ultrasound evidence of synovitis with significantly reduced effusion relative to placebo.

Participants

Participants will be males and females between the ages of 18 and 40 who are undergoing surgery for a MLKI and fit all inclusion and exclusion criteria (Table 1). Those with reduced or altered capacity due to administration of any mind-altering substances such as tranquilizers, conscious sedation or anesthesia, brain injury, or age outside of the targeted range will not be recruited for participation in this study. Potential study participants will be referred to members of the research team during regularly scheduled office visits with the participating study physicians or their physician assistants at the three study sites.

Table 1.

Inclusion and exclusion criteria for entrance into the LION clinical trial for patients with MLKI

Inclusion criteria

Age 18 to 40 years

MLKI defined as a complete grade III injury of 2 or more ligaments

Planned surgical reconstruction and/or repair

Willingness to comply with the study protocol and assessments

Exclusion criteria

Allergic to any active or inactive ingredient of losartan

Pregnant, planning to become pregnant, or sexually active females choosing not to use effective means of contraception during the 30-day course of losartan

Those at increased risk of losartan related side effects including those with severe renal insufficiency, hepatic disease, hypotension, and/or hyperkalemia

Have a history of prior knee ligament surgery of the involved knee

Have a traumatic brain injury that limits their ability to participate in their postoperative care or any condition that would preclude the ability to comply with postoperative rehabilitation

Have a concomitant injury or underwent a surgical procedure that will preclude the ability to perform range of motion exercises (i.e. surgery for extensor mechanism rupture or avulsion, vascular graft surgery)

Design

The LION Trial is a parallel group, double-blind, placebo-controlled superiority clinical trial that is designed to investigate the efficacy of a 30-day postoperative course of losartan following MLKI reconstruction. Enrollment began in the fall of 2025 and will continue through the fall of 2028. This study will take place at two academic medical centers one military medical center located across the United States. The full list of study sites and recruitment status is available at ClinicalTrials.gov (NCT06933706). Mass General Brigham is acting as the central IRB for the study (IRB #2025P000672), with oversight provided by the Defense Health Agency’s Office of Human Research Oversight. The SPIRIT reporting guidelines have been followed in the production of this manuscript, and the complete SPIRIT checklist for the LION Trial will be made available as an additional file (Appendix A) [32].

Randomization, group allocation, and blinding

Randomization

Following enrollment in the study, participants will be randomized. The allocation sequence will be generated by one of the study statisticians (GH) using R statistical software (Version 4.4.3; R Foundation for Statistical Computing; Vienna, Austria). Randomization will be stratified by site, with distinct randomization schedules generated for each site. Permuted blocks of size four will be used to maintain an approximate 1:1 allocation between treatment and placebo groups. Site-specific detailed randomization lists will be held by an unblinded statistician and will not be accessible to investigators enrolling participants. The statistician will directly distribute randomization schedules to the Investigational Drug Services at each site. After each participant has completed baseline testing, research personnel will contact the IDS via email so that the participant can be randomized. The IDS will then assign the next sequential allocation based on the site-specific randomization schedule and dispense the blinded study medication for distribution to the participant.

Blinding

Patients, treating physicians, the study PI, assessors, and the statistician performing the data analysis will be blinded to group assignment. At each site, one member of the research team will be unblinded to allow for communication with each site’s Investigational Drug Service and to respond should unblinding be required due to an Adverse Event. This person will not be involved with the consent process, data collection, or data analysis. Blinding of the medication will be accomplished by over-encapsulating the losartan capsules and creating matching placebo capsules.

Intervention

Losartan

Losartan is FDA-approved medication that is widely used to treat hypertension in adults and children greater than 6 years old, to reduce the risk of stroke and left ventricular hypertrophy, and to treat diabetic nephropathy for patients with type 2 diabetes who have elevated serum creatinine and proteinuria [33]. The Agency for Healthcare Research and Quality’s Medical Expenditure Panel Survey indicated that losartan was the 9th most prescribed medication in the U.S. with more than 12 million individuals filling prescriptions in 2020 alone [34].

Mechanism of action

Losartan is an angiotensin-II inhibitor that modulates the rennin-angiotensin system by blocking the activation of angiotensin type I receptors, thus preventing binding with angiotensin-II and decreasing blood pressure [35, 36]. Losartan has a broader therapeutic potential for muscle healing and treatment for diseases ranging from rheumatoid arthritis, osteoarthritis, chronic kidney disease, Marfan syndrome, and fatty liver [21, 36–40]. As previously described, TGF-β plays an active role in fibrosis, leading to the formation of adhesions and scar tissue. Losartan has been shown to inhibit TGF-β signaling by both down-regulating pSMAD2/3 and upregulating the protective protein peroxisome proliferator-activated receptor gamma, thereby reducing fibrosis, attenuating cartilage loss, and lessening pain behaviors [21, 22, 41]. By inhibiting TGF-β signaling through multiple mechanisms, losartan reduces pain, myofibroblast activity, synovitis, fibrosis, and cartilage degeneration in multiple animal models.

Dosage, duration, and timing

The standard route of losartan administration is an oral tablet taken 1–3 times daily, and dosage varies from 25 to 100 mg daily. Studies of normotensive individuals have not reported medication-related adverse events or hypotension associated with losartan daily doses ranging from 25 to 100 mg/day [42, 43]. The LION Trial will utilize a daily dose on the lower end of this range (25 mg/day) to mitigate potential complications. The daily dose of 25 mg of oral losartan is consistent with other ongoing trials involving losartan and orthopaedic patient populations (NCT04212650: 25 mg/day × 30 days, NCT04815902: 25 mg/day × 30 days, NCT02263729: 50 mg/day × 4 weeks).

Administration of study drug

The FDA has granted the LION Trial an IND exemption (PIND 167593). Losartan potassium tablets will be sourced for the study and will be over-encapsulated with #0 hard gelatin capsules using microcrystalline cellulose filler. The oral placebo will be the same hard gelatin capsule with only cellulose filler. Upon completion of the trial, any unused study medication will be destroyed by each site’s investigational pharmacy.

The appropriate dose and number of capsules will be placed in an unmarked pill bottle, and patient-specific instructions will be printed and adhered to the bottle. A separate, printed instruction sheet will also be given to each participant. The label and printed instructions will include contact information for one of the unblinded personnel should they have any questions about dosing instructions. The investigational labels will meet the requirements listed in 21 CFR 312.6 and will include the statement, “Caution: New Drug-Limited by Federal (or United States) law to investigational use” on the label. Losartan and placebo capsules will be stored at room temperature. Participants in the study will be dispensed the full 30-day allotment on the day of surgery.

Potential risks of losartan

Common adverse reactions to losartan include upper respiratory infection (8%), dizziness (3%), nasal congestion (2%), back pain (2%), sinusitis (1%), muscle cramping (1%), and leg pain (1%). Per the FDA’s guidance, female participants of childbearing age will be informed about the consequences of exposure to drugs that act on the renin-angiotensin system during the second- and third- trimesters. Female participants will also be informed that these consequences do not appear to result from intrauterine drug exposure that has been limited to the first trimester. Because female participants are required to have a negative pregnancy test prior to starting the study drug, and because the duration of use is 30 days, intrauterine drug exposure could only occur during the first trimester. Participants will be asked to report pregnancies to their physicians and the study team as soon as possible. Also, participants will be instructed not to use potassium supplements or salt substitutes containing potassium without consulting their physician.

Mitigation of losartan risks

To mitigate the potential risk of symptomatic hypotension in normotensive individuals, blood pressure will be assessed at study entry. Blood pressure will also be monitored remotely while taking the study medication. Patients will be advised of the symptoms of hypotension and instructed to seek medical attention for such symptoms. If a patient develops clinically significant hypotension at any point, defined as a greater than 20% drop in systolic blood pressure relative to baseline, they will be instructed to immediately discontinue losartan treatment. Breaking the randomization code will be performed by the study’s medical officer and will occur if it is necessary for the care of the subject. For example, if an adverse event or serious adverse event occurs with a subject and knowledge of the drug randomization would be important for clinical care or to determine appropriate treatment, then the medical director will break the code. Further details about adverse event evaluation and classification can be found under “Adverse Events.”

Medication adherence

Adherence to the treatment protocol will be assessed and verified through the completion of the drug log. The drug log will be maintained by unblinded study personnel and inspected on no less than an annual basis by an unblinded study co-investigator. Patient adherence to the medication will be documented through pill counts where the patient will be asked to bring the pill bottle with them to research visits. Participants will be asked to take 1 pill daily during the 30-day prescription; thus, 1 day will equate to 1 pill. The number of pills remaining at the 1-month research visit will be divided by the total number of days in which the patient was prescribed to take the medication. Losartan treatment will be considered feasible and acceptable if over 70% of participants reach the threshold of taking 80% of the prescribed medication [44]. We will calculate the proportion of patients who meet this criterion in the treatment group as well as the 95% CI around this compliance rate.

Outcome measures (Table 2)

Table 2.

Five elements of LION Trial outcome measures

Primary outcome
Outcome	Domain	Measure	Metric	Method of aggregation	Time point
Cincinnati Occupational Rating Scale (CORS)	Activity level	CORS Questionnaire (0–60)	CORS scores at each time point	Mean ± standard deviation or median [interquartile range] at each time point*	Baseline 30 days 6 months 12 months
Secondary outcomes
Outcome	Domain	Measure	Metric	Method of aggregation	Time point
Time to Return to Duty/Work/Sport	Return to activity	Self-reported date of return to activity	Time of surgery to return to activity	Median time of first return to activity; proportion returned by 12 months	Biweekly from 6 to 12 months
IKDC Subjective Knee Score	Patient-reported pain and function	IKDC Subjective Knee Score (0–100)	IKDC scores at each study time point	Mean ± standard deviation or median [interquartile range]*	Baseline 30 days 6 months 12 months
VAS Pain Score	Pain level	Visual Analog Scale (worst, best, average pain in past 24 h)	VAS Pain Scores at each study time point	Mean ± standard deviation or median [interquartile range]*	Baseline 30 days 6 months 12 months
Medication Adherence	Treatment adherence	Pill count (% of 30 pills taken)	Adherence over intervention period	Proportion of participants > 80% adherent	30 days
Knee Range of Motion	Knee function	Degrees of flexion or extension measure with goniometer	Knee range of motion at each time point	Mean ± standard deviation or median [interquartile range]*	Baseline 30 days 6 months 12 months
Quadriceps Strength	Muscle strength	Peak torque measured with dynamometer (% index of contralateral limb)	Strength symmetry at time points	Mean ± standard deviation or median [interquartile range]*	6 months 12 months
Synovitis Grade	Knee inflammation	Imaging grading on a scale of 0–3	Severity of synovitis	Proportion of participants with each grade	30 days 6 months 12 months

^*Depending on tests of normality either mean or median will be used

The primary outcome variable for the LION Trial is the CORS Score. All other outcome measures are secondary, including the time to return to active duty, work, and/or sport after surgery; IKDC Subjective Knee Scores; VAS Pain Scores; knee ROM; quadriceps strength; and ultrasound measures of persistent synovitis (superb microvascular imaging and synovial thickening). Detailed descriptions of each variable and the data collection methods that will be used to achieve each of the three study aims are described below:

• Aim 1: Determine if a 30-day postoperative course of losartan improves the ability to return to duty, work, or sports and patient-reported outcomes when compared to placebo following MLKI.

  Patients will be asked to complete patient-reported outcome questionnaires (CORS, IKDC Subjective Knee Form, and VAS) at baseline, 30 days post-operatively, 6 months post-operatively, and 12 months post-operatively. The primary outcome variable for the LION Trial is the CORS Score which will be used to quantify activity after surgical treatment of MLKI. The CORS Questionnaire was developed and validated to assess work status across knee conditions. The CORS Questionnaire is a valid and reliable 7-item scale that quantifies the hours or number of times a patient performs the following activities: sitting, standing/walking, walking on uneven ground/turning/twisting, climbing, squatting, and frequency of lifting/carrying and the pounds carried [45, 46]. Scores range from 0 to 60 with greater scores being indicative of more strenuous work activities. The CORS Score has demonstrated excellent reliability (ICCs ranging from 0.87 to 0.97) [46].

  Secondary outcome measures will include the time to return to active duty, work and/or sport; the IKDC Subjective Knee Score; and the VAS Pain Score. Beginning 6 months after surgery, patients will be contacted biweekly via their self-selected method (phone, text, or email) to determine the date that they return to work and/or sport. We have successfully employed these methods in a previous prospective study assessing return to play after ACL reconstruction with greater than 90% response rates [47]. The IKDC Subjective Knee Score has been shown to be valid, reliable, and responsive, and has been previously used to assess outcomes following MLKI procedures [48–50]. The IKDC Subjective Knee Score has excellent test–retest reliability (ICC = 0.94), and the score associated with the Patient-Acceptable Symptom State is 75.9 points [48, 51]. The IKDC Subjective Knee Score has also been demonstrated to correlate well with other measures of physical function (r-values ranging from 0.47 to 0.66) [48]. The VAS Pain Score will be used to assess pain at each study time point. Patients will be asked to rate their pain on a 10 cm scale in 3 different scenarios: worst pain in the past 24 h, best pain in the past 24 h, and average pain in the past 24 h. The test–retest reliability of the VAS Pain Score is excellent (ICC = 0.97), with a Minimal Clinically Important Difference of 0.88 cm in a sample of patients with knee ligament injuries [52, 53].

• Aim 2: Assess whether losartan results in more symmetric knee range of motion and quadriceps strength following MLKI when compared to placebo.

  At baseline, 30 days post-operatively, 6 months post-operatively, and 12 months post-operatively, active ROM will be assessed bilaterally using a long-arm goniometer. When measuring knee extension, participants will be positioned supine with the heels elevated on a bolster to allow for hyperextension. Goniometry remains the gold standard for assessing knee ROM with standard errors of measurement ranging from 1 to 2° [54, 55]. Our team has performed ROM testing for more than 10 years across a number of projects, showing excellent test–retest reliability (ICC = 0.92) [56]. ROM will be collected by blinded research personnel at each site, and all predesignated examiners will be trained by the PI prior to initiating the study as part of the site initiation visit.

  Quadriceps strength will be assessed using an isokinetic dynamometer at 6 and 12 months post-operatively. Participants will be in a seated position with the test knee flexed to 90°. The dynamometer lever arm will be placed 3 cm proximal to the lateral malleolus. Following 3 practice trials, 3 test repetitions will be performed at 90°/s with peak torque averaged across the 3 trials and normalized to body mass (Nm/kg). To account for potential measurement differences between the dynamometers used at the three sites, quadriceps strength of the operative limb will be expressed as a percentage of the contralateral limb.

• Aim 3: Compare ultrasound measures of synovitis and effusion between groups treated with losartan versus placebo following surgical treatment of MLKI.

  Participants will get ultrasounds 30 days post-operatively, 6 months post-operatively, and 12 months post-operatively. Following the standardized Outcome Measures in Rheumatoid Arthritis Clinical Trials guidelines [57], diagnostic medical sonographers experienced with ultrasound knee assessment or physicians certified in musculoskeletal sonography will perform a dynamic ultrasound scan. Superb microvascular imaging (SMI) visualizes smaller, slower velocity vessels, and will be used to assess synovitis [58, 59]. Longitudinal suprapatellar scans will be acquired in three standardized regions (medial, midline, and lateral) with participants supine in 30° of knee flexion.

  The presence and severity of synovitis will be graded by a blinded, fellowship-trained musculoskeletal radiologist according to the European League Against Rheumatism and Outcome Measures in Rheumatology—Outcome Measures in Rheumatoid Arthritis Clinical Trials guidelines [60], which were then adapted for use when assessing SMI images [61]. No SMI activity will be considered Grade 0 (no synovitis), up to three single SMI spots will be considered Mild (Grade 1), more than three spots but with SMI signal filling < 50% of the grayscale background will be considered Moderate (Grade 2), and SMI signal filling > 50% of the grayscale background will be considered Severe (Grade 3). Ultrasound measures of synovitis have been found to be reliable and responsive after treatment and have demonstrated construct validity when compared to MRI measures of synovitis [62–65].

  B mode images of the suprapatellar recess using longitudinal probe orientation in line with the quadriceps tendon will be used to assess effusion. The absence of joint capsule distension will be considered Grade 0 (No effusion). Grade 1 (Mild) effusion will be defined as the presence of small anechoic region or hypoechoic beneath the capsule or minimal capsular distension. Grade 2 effusion (Moderate) will be characterized by capsular elevation or distension parallel to the joint. Bulging or convex capsular distension will be categorized as Grade 3 (Severe) effusion [57, 60, 66].

Participant timeline

Participants will be seen at five time points (preoperatively, on the day of surgery, 30 days postoperatively, 6-months postoperatively, and 12 months postoperatively) as detailed in the SPIRIT participant timeline figure (Table 3) [67].

Table 3.

Schedule of enrollment, interventions, and assessments for the LION Trial

^aDay before clinic visit to the day before surgery

^b21–42 days after date of surgery

^c5–7 months after date of surgery

^d11–14 months after date of surgery

^eCORS Questionnaire, Visual Analogue Scale for pain, and IKDC Subjective Knee Form

Visit 1 (preoperative) may occur at a participant’s regularly scheduled clinic visit prior to surgery or at a separate study visit prior to surgery. At this visit, the subject will undergo a final eligibility screening and sign informed consent (Appendix B). They will also complete the CORS Questionnaire and the IKDC Subjective Knee Form, as well as active knee range of motion measurement. Participants will be randomized into either the losartan or placebo group within seven days prior to surgery to ensure that Investigational Drug Services have time to dispense the study drug.

Visit 2 (day of surgery) is on the day of surgery. For participants who are able to become pregnant, we will require a negative pregnancy test before beginning the study drug. This is often performed prior to surgery according to each site’s clinical policies and procedures. If not required clinically, research personnel will administer a certified urine pregnancy test and only continue if the test is negative. If the test is positive, the patient will be informed of this result and excluded from the study. Any intraoperative findings will be noted, and the subject will be instructed to start taking their study drug the day after surgery.

Visit 3 (30 days postoperative) will be completed after taking the oral intervention for 30 days. The subjects will complete all questionnaires, ROM testing, and ultrasound imaging.

Visit 4 (6 months postoperative) will include all questionnaires, ROM testing, quadriceps strength testing, and ultrasound imaging.

Visit 5 (12 months postoperative) will include all questionnaires, ROM testing, quadriceps strength testing, and ultrasound imaging.

Participation compensation

To promote attendance, patients will be contacted by phone both 1 week and 1 day prior to their study visits. Participants will be compensated $50 for attending each postoperative study visit involving ultrasound assessments ($150 total compensation). Because funding for the proposed trial is from a federal source, active-duty military personnel cannot be compensated for their participation.

Potential problems and alternative strategies

Postoperative physical therapy

Variable physical therapy regiments and locations across the study population may limit the ability to assess the effect of losartan on MLKI outcomes. As such, participants and their treating physical therapists will be given printed manuals with standardized, milestone-based rehabilitation guidelines. The rehabilitation guidelines will also be made available on the study-dedicated website. The number of physical therapy sessions attended by each participant will be recorded and can be used as covariate in the statistical analyses.

Enrollment

We will be enrolling from enrolling physicians’ practices at the three study sites. We routinely collaborate with physicians at these locations on clinical research projects, and all sites have embedded research personnel to assist with enrollment and data collection.

Minimizing attrition

To maximize retention, all study visits can be scheduled to coincide with physician follow-up appointments. Participants will be asked to provide alternate contacts and to specify whether study staff may leave messages or send mail. The research coordinators and the site PIs will track all study visits and will follow-up on any missed visits. Proactive strategies will be developed to work with participants who have trouble attending study visits. Participants will have 7:30 am–5 pm access to research personnel.

Statistical methods

Sample size justification

The primary outcome variable for this trial is the CORS Score at 1 year. Assuming a standard deviation of 19.6 points, a sample size of 38 participants per group will provide at least 80% power to detect a difference of at least 12.8 points between groups [68]. Note that this is a conservative power analysis, as our statistical analysis plan will use mixed models to account for correlations across time points. Allowing for up to 15% of subjects being lost to follow-up, an additional 7 participants will be enrolled per group (45 participants per group; 90 total).

Outcome measures

The primary analysis of the study will be ITT (intention-to-treat), where each participant will be analyzed according to the randomization assignment, regardless of treatment received. The ITT set will include all participants randomized. The per-protocol set will include all participants randomized with greater than 80% adherence to the assigned intervention, assessed via pill count. The primary analysis will be on the ITT set. Secondary analyses will be conducted on the per-protocol set.

For each of the aims, a mixed model will be used to identify differences in continuous measures between groups across the study time points, after adjusting for covariates as needed (age, biological sex, body mass index, MLKI injury pattern, number of physical therapy sessions attended). Hypothesis testing will focus primarily on the time by study group interaction; if not significant, the interaction effect will be removed, and main effects will be evaluated. Model assumptions, including normality, will be assessed using a combination of visual plots and formal testing, with remedial measures employed as needed. Akaike Information Criterion and likelihood ratio testing will be used to determine appropriate covariance structures for each model. Categorical variables (return to active duty, return to work, return to sport, and the incidence of synovitis and synovial hypertrophy) will be compared between groups using chi-square or Fisher Exact tests as appropriate, or using logistic regression for covariate adjustment as needed. Multiple testing corrections adjustments will be used as needed; however, the type of method employed will be context- and analysis-specific.

Protocol non-adherence and missing data

We do not anticipate a considerable volume of missing data and have powered the study to allow for 15% dropout. We will describe dropout and other forms of missing data by reporting the number of participants that drop out in each group, the reasons for dropout, and the timepoint of dropout. We will assess whether the frequency of these dropouts differs between treatment groups. We will examine the distribution of baseline clinical and demographic in participants dropping out compared to those completing the study.

Secondary analyses will be conducted on data imputed under the missing at random assumption, whereby missing data will be imputed based on observed covariates and outcomes. Multiple imputation will be used to impute missing data. To more accurately reflect the uncertainty in missing values, multiple imputation involves the creation of multiple versions of the dataset, with missing values imputed under an assumed distribution, and then averaging results across these datasets. For the continuous outcomes we will impute data by fully conditional specification, and imputation will be conducted separately by treatment group. Imputation models will include the baseline CORS Score and other baseline demographic and clinical characteristics. The use of multiple imputation will not be guided by the proportion of missing data; however, the number of imputations will be guided by the fraction of missing information [69, 70].

Interim analysis

No formal interim efficacy analyses or stopping guidelines are planned for this trial. Safety monitoring will be conducted throughout, with adverse events reported to the site IRB and the Defense Health Agency’s Office of Human Research Oversight. Study drug may be discontinued for individual participants if clinically significant adverse effects occur. Any decision to terminate the trial early would be made by the principal investigator in consultation with the IRB and oversight bodies. Interim results will not be available to investigators, participants, or assessors to preserve trial integrity.

Discussion

Although surgical reconstruction can improve clinical outcomes for individuals who suffer from MLKIs, a significant portion of patients are nevertheless unable to recover sufficiently to perform active military duty, high-level sports, or routine daily tasks [6, 7]. This is at least partially due to the prolonged and exaggerated inflammatory response that coincides with MLKIs and the subsequent surgical intervention that exacerbates arthrofibrosis and reduces ROM [19, 71]. As such, there is a growing need for a therapeutic intervention that reduces the inflammatory environment of MLKIs, thereby improving both functional and clinical outcomes. The goal of the LION Trial is to investigate the efficacy of a 30-day postoperative course of losartan, a widely used angiotensin II receptor blocker, in improving rates of return to activity, increasing ROM and quadricep strength, and rescuing joint capsule integrity following MLKI reconstruction.

While inflammatory markers and growth factors are a natural and even expected part of the healing process, the prolonged and amplified nature of these pathways following a MLKI may be a biophysiological overcorrection that promotes protection over practicality [72]. Losartan may mitigate arthrofibrosis after MLKIs by downregulating TGF-β signaling associated with arthrofibrosis as well as pro-inflammatory cytokines like IL-6 that are associated with pain and ROM loss in ligamentous reconstruction [10, 19]. In turn, the use of losartan has the potential to not only reduce the need for further surgical interventions, such as manipulation under anesthesia, but may also promote a faster return to preoperative activity levels. While these benefits have been substantiated in animal models and through preliminary clinical data, no prior study has explicitly investigated the efficacy of losartan for MLKI by leveraging a randomized, placebo-controlled trial.

This study protocol will holistically evaluate the effect of losartan after MLKI by quantifying both subjective and objective aspects of MLKI recovery. The CORS Score will measure the patient’s perceived ability to return to activity, whereas ROM, strength testing, and sonographic assessments will provide objective and clinically relevant measures of postoperative recovery and the potential mechanisms of losartan to improve outcomes. While we hypothesize that losartan will improve all of these outcome measures, using multiple variables to assess MLKI outcomes will ensure congruity between patient perception and clinical manifestation, which is not always the case in orthopaedic research [73]. As such, this study has the potential to redefine perioperative management and improve long-term functional outcomes for patients undergoing MLKI reconstruction by providing a low-cost intervention with a long track record of clinical safety.

Trial status

This is protocol version 6.0 (October 8, 2025). Patient recruitment began in November 2025 with recruitment anticipated to end in August 2028.

Oversight and monitoring

Personnel

This innovative work requires a team science approach, and our multidisciplinary investigative team is uniquely poised to complete this important military-civilian collaborative project. We have performed the foundational work to identify risk factors and underlying mechanisms of poor outcomes in this group, and our team members currently collaborate on several ongoing clinical trials. The team includes a clinical trialist and expert on biological factors contributing to patient-reported outcomes after knee injury (CJ), clinician scientists with backgrounds in the biological mechanisms of postoperative complications and posttraumatic osteoarthritis (CL, AS, LZ), an implementation scientist (CC), a statistician with experience working with complex datasets and specifically with knee-related clinical trials (GH), and experts in ultrasound assessments of synovitis (SS, XY).

Quality control

Quality Control (QC) procedures will be implemented beginning with the data entry system and data QC checks that will be automatically generated to run on the database. These checks will be reviewed by the study statistician, GH. All missing data and data anomalies will be communicated for clarification/resolution. Internal audits will be scheduled quarterly to review the study source documents and assess data collection. The informed consent form signatures will be reviewed, data entered in the study documents will be verified against the data collection records, and an investigator will audit a data collection. Additionally, we will utilize a clinical monitor, MZ of MGB Sports Medicine, to ensure data quality. MZ will act as a clinical monitor to independently verify that the clinical trial is conducted, data are generated, documented (recorded), and reported in compliance with the protocol and International Conference on Harmonization Good Clinical Practice. We receive audits from MZ, and she will perform post audit reviews of our procedures with an emphasis on addressing any deficiencies. We will provide direct access to all trial related sites, source data/documents, and reports for the purpose of monitoring and auditing by the sponsor, and inspection by local and regulatory authorities.

Adverse events

The Principal Investigator (CJ) and the physician identified as the medical director at each site (CL, AS, LZ) will assess the occurrence of adverse events throughout the subjects’ participation in the study. These events will be monitored systematically at the 30-day, 6-month, 12-month, and 24-month study visits and non-systematically through routine surgical board screening, medical care with participating physicians, and spontaneous patient reporting. Adverse events are defined as a patient care event in which a patient has experienced a treatment-related injury or death, or in which there is a risk of such injury or death. Adverse events may or may not have been preventable and may (or may not) be related to use of medication or a medical device in diagnosis, treatment, prevention, or monitoring of a patient’s disease or condition. To ensure standardization of adverse event classification, all adverse events will be categorized as either unexpected or expected; definitely, probably, possibly, or not related to intervention; and non-serious or serious by the Principal Investigator and site medical director. Severity will also be graded from 1 to 5 as described by the CTCAE v5 AE reporting system [74].

Subjects will be followed from the time of randomization to 30 days after study participation has been discontinued or until death, whichever occurs first. The clinical course of each event will be followed until resolution, stabilization, or until it has been determined that the study participation is not the cause. The investigator is responsible for ensuring that all adverse events observed by the investigator or reported by the subject are fully recorded in the subject’s case report form, the subject’s medical records, and/or in any other institutionally required documentation. Source documentation must be available to support all adverse events. All adverse events will be recorded in a centralized log, and all adverse events will be reported to the central IRB consistent with IRB policy.

Data monitoring

A Data Safety and Monitoring Board (DSMB) will meet biannually to ensure participant safety and data integrity throughout the entirety of the study. The DSMB is composed of an orthopaedic surgeon, physical therapist, emergency medicine physician, and biostatistician, all of whom have collective expertise on musculoskeletal injuries, are familiar with monitoring clinical projects, and are independent of the study team and the Department of Defense. The LION Trial was approved by the DSMB prior to the enrollment of the first participant, and the DSMB will make recommendations to the study team and the Department of Defense including, but not limited to, whether the study should be permanently stopped, modified, or continue unchanged. All adverse events will be shared with the DSMB to inform decision-making about any potential study modifications that must be made to uphold patient safety.

Provisions for post-trial care

If a participant suffers harm directly from participation in the LION Trial, the care needed to treat the injury will be provided. In this event, the hospital sites will reserve the right to bill the patient’s insurance company or other third parties, if appropriate, for the care for any study-induced injuries. The study team will try to have these costs paid for, but the patient may be responsible for some of them. For example, if the care is billed to the patient’s insurer, they will be responsible for payment of any deductibles and co-payments required by their insurer. Additionally, there are no plans to pay patients or otherwise provide them with compensation in the event an injury occurs. If at any time a patient believes they have been injured or have experienced a medical problem as a result of taking part in the research study, the patient will be told to contact principal investigator (CJ) as soon as possible.

Data collection and management

Availability of data and materials

In accordance with the Congressionally Directed Medical Research Programs policy on sharing data and research resources, Final Research Data will be made available under the auspices of the Principal Investigator (CJ). Upon completing a data share agreement, requestors will be granted access to the Final Research Data file posted on the Harvard Dataverse Repository website as described below. Intellectual property, although not expected, and data generated as part of this project will be governed by Mass General Brigham and United States Army Medical Research Development and Command policies as outlined in Congressionally Directed Medical Research Programs: Policy on Sharing Data and Research Resources.

Types of data produced

A rich dataset will be created which will include patient demographic information, patient-reported outcomes, isokinetic strength, range of motion, and ultrasound assessments of knee synovitis as described under “Outcome Measures.” Data will be collected from 90 participants after surgical treatment of MLKI and will be stored in the Harvard Dataverse Repository.

Demographic information will include patient age, sex, race, ethnicity, body mass index, injury history, intraoperative findings, and surgical treatment. Patient-reported outcomes will include the CORS Scores, IKDC Subject Knee Form Scores, and VAS Pain Scores, and all participant responses will be stored in a study-specific, password-protected REDCap project. Ultrasound image grading and knee strength testing results will also be stored in the study’s REDCap project.

All data will be deidentified and will be stored on secure, password-protected computers. Each variable in the dataset will have an accompanying text file describing the variable, the unit of measure, the time points that the variable was collected, and an explanation of coding for categorical variables. Variable descriptions will be provided to prevent misuse, misinterpretation, or confusion.

Conditions for access and sharing

As part of the consent process (Appendix B) for the LION Trial, all participants will provide informed consent for the use of their data in future publications and ancillary studies. The project team will make the data of the LION Trial available as widely and as freely as possible while safeguarding the privacy of participants and protecting confidential and proprietary data. Furthermore, any research resources will be shared in line with the policies adopted by the Department of Defense for the purposes of this grant. Data will be made publicly available, and requestors will be required to complete a data-sharing agreement the Principal Investigator’s (CJ) institution. The purpose of the data-sharing agreement is to ensure data security at the recipient site and clarify that manipulating the data for the purposes of identifying subjects is strictly prohibited. No limits or caveats for co-authorship will be required as a precondition for receiving data.

Conditions and provisions for reuse, redistribution, and derivatives

The investigators require appropriate use of the Final Research Data file by the scientific community. Publication guidelines will be implemented to ensure appropriate citation and acknowledgment of the LION Trial research group as the source of the data used in publications, promote collaboration, assist investigators in avoiding unintended duplication of effort, and foster high quality and creative publications based on valid use and interpretation of the data.

Plans for archiving and preservation

All project data will be retained for a minimum of seven years following closeout of the project, in accordance with policies adopted by United States Army Medical Research Development and Command and National Institute of Health (NIH). The Final Research Data file (comma separated file) and variable descriptions (pdf files) will be uploaded to the Harvard’s public repository, Dataverse. The Harvard Dataverse captures, stores, organizes, and provides open and stable worldwide access to the institution’s intellectual capital. It facilitates reuse or deposited materials to the extent warranted by copyright law or by the licensing terms of the concerned material. Other policies, including local, state and federal laws and the Privacy Rule under the Health Insurance Portability and Accountability act will be adhered to when providing such data.

Abbreviations

LION

Losartan to Improve Outcomes after multi-ligament kNee injury

MLKI

Multi-ligament knee injury

ROM

Range of motion

ACL

Anterior cruciate ligament

TGF-β

Transforming growth factor beta

TKA

Total knee arthroplasty

IL-6

Interleukin-6

IKDC

International Knee Documentation Committee

VAS

Visual Analog Scale

CORS

Cincinnati Occupational Rating Scale

SMI

Superb Microvascular Imaging

ITT

Intention-To-Treat

NIH

National Institute of Health

DSMB

Date Safety and Monitoring Board

Authors’ contributions

CJ is the Principal Investigator; he conceived the study in conjunction with the Department of Defense, leading the proposal and protocol development as well as the production of the manuscript. SK led the writing of the manuscript. GH organized the statistical analysis plan and sample size calculations. All other authors participated in conceptualization of the protocol; developed methods; and critically read, improved, and approved of the final manuscript. No professional writers were involved in the production of this manuscript.

Funding

The project is funded by the Department of Defense (Award number: HT9425-25–1-0977) with additional support by the NIH National Center for Advancing Translational Sciences through grant numbers UM1TR004408 and UL1TR001998. The Department of Defense contact person for this trial is Akua Roach, PhD (Program Manager, Peer Review Orthopedic Research Program, The Congressionally Directed Medical Research Programs, akua.roach.civ@health.mil). The content is solely the responsibility of the authors and does not necessarily represent the official views of the Department of Defense or NIH. The Department of Defense and the NIH did not have a role in the design of the study, collection, analysis, or interpretation of data, or writing the manuscript.

Data availability

In accordance with the Congressionally Directed Medical Research Programs policy on sharing data and research resources, Final Research Data will be made available under the auspices of the Principal Investigator (CJ). Upon completing a data share agreement, requestors will be granted access to the Final Research Data file posted on the Harvard Dataverse Repository website as described below. Intellectual property, although not expected, and data generated as part of this project will be governed by Mass General Brigham and United States Army Medical Research Development and Command policies as outlined in Congressionally Directed Medical Research Programs: Policy on Sharing Data and Research Resources.

A rich dataset will be created which will include patient demographic information, patient-reported outcomes, isokinetic strength, range of motion, and ultrasound assessments of knee synovitis as described under “Outcome Measures”. Data will be collected from 90 participants after surgical treatment of MLKI and will be stored in the Harvard Dataverse Repository.

Demographic information will include patient age, sex, race, ethnicity, body mass index, injury history, intraoperative findings, and surgical treatment. Patient-reported outcomes will include the CORS Scores, IKDC Subject Knee Form Scores, and VAS Pain Scores, and all participant responses will be stored in a study-specific, password-protected REDCap project. Ultrasound image grading and knee strength testing results will also be stored in the study’s REDCap project.

All data will be deidentified and will be stored on secure, password-protected computers. Each variable in the dataset will have an accompanying text file describing the variable, the unit of measure, the time points that the variable was collected, and an explanation of coding for categorical variables. Variable descriptions will be provided to prevent misuse, misinterpretation, or confusion.

As part of the consent process (Appendix B) for the LION Trial, all participants will provide informed consent for the use of their data in future publications and ancillary studies. The project team will make the data of the LION Trial available as widely and as freely as possible while safeguarding the privacy of participants and protecting confidential and proprietary data. Furthermore, any research resources will be shared in line with the policies adopted by the Department of Defense for the purposes of this grant. Data will be made publicly available, and requestors will be required to complete a data-sharing agreement the Principal Investigator’s (CJ) institution. The purpose of the data-sharing agreement is to ensure data security at the recipient site and clarify that manipulating the data for the purposes of identifying subjects is strictly prohibited. No limits or caveats for co-authorship will be required as a precondition for receiving data.

The investigators require appropriate use of the Final Research Data file by the scientific community. Publication guidelines will be implemented to ensure appropriate citation and acknowledgment of the LION Trial research group as the source of the data used in publications, promote collaboration, assist investigators in avoiding unintended duplication of effort, and foster high quality and creative publications based on valid use and interpretation of the data.

All project data will be retained for a minimum of seven years following closeout of the project, in accordance with policies adopted by United States Army Medical Research Development and Command and National Institute of Health (NIH). The Final Research Data file (comma separated file) and variable descriptions (pdf files) will be uploaded to the Harvard’s public repository, Dataverse. The Harvard Dataverse captures, stores, organizes, and provides open and stable worldwide access to the institution’s intellectual capital. It facilitates reuse or deposited materials to the extent warranted by copyright law or by the licensing terms of the concerned material. Other policies, including local, state and federal laws and the Privacy Rule under the Health Insurance Portability and Accountability act will be adhered to when providing such data.

Declarations

Ethics approval and consent to participate

All materials and methods regarding this study have been analyzed and approved by the Institutional Review Board at Mass General Brigham (IRB#: 2025P000672). All procedures are in agreement with the principles expressed in the Declaration of Helsinki. Participants will be informed about the scope and procedures of the study and will be asked to sign an informed consent by a member of the research staff before starting the initial evaluation.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.