The purpose of the study is to assess the longitudinal post-operative care effects of protein supplementation on muscle atrophy in the post-operative period following ACL reconstruction. The main outcome will be muscle size/mass as measured using dual energy x-ray absorptiometry (DEXA) scanning. The primary objective is to assess for any beneficial impact of protein supplementation, with implications of standardizing a recommended protocol for protein supplementation after ACL reconstruction.

Secondary outcomes will be to evaluate the survey data from the KOOS JR and Tampa Scale surveys, as well as functional measures recorded during physical therapy.

This study is designed to evaluate non-interventional longitudinal post-operative clinical improvement. The proposed study is a randomized non-interventional, double blind study. Subjects will include patients age 16 to 40 undergoing primary ACL reconstruction for an acute ACL tear. Demographic information including age, sex, BMI, and sport participation will be obtained from patients at the time of recruitment.

Subjects will be randomized to one of three categories: 1)placebo, 2)protein supplementation, or 3)protein supplementation with amino acids. The probability is is a 1 in 3 chance to be enrolled in each group. Participants will be provided the supplement drink immediately following surgery and will be asked to consume the supplement 2-times daily following ACL reconstruction for a total of 12 weeks post-op. In addition, participants will be asked to complete a weekly food diary in which they track their diet for 2 week days and 1 weekend day each week for all 12 weeks. This will help account for dietary proteins. Subjects will also be asked to complete the KOOS Jr and Tampa Scale surveys (attached in the application) through Houston Methodist's Redcap system at each time point (Pre-op, 4, 8 and 12 weeks postop).

Briefly, BCAAs (particularly leucine) represent primary triggers for the stimulation of protein synthesis via signaling through the mammalian target of rapamycin complex 1 pathway (mTORC1) in skeletal muscle and other tissues. Whey hydrolysate is a complete protein source that is considered to be "fast absorbing." Casein is a complete protein source that is "slow absorbing" relative to whey.9 All protein sources used in this investigation are commercially available nutritional supplements. The placebo will include a crystallite drink.

Standard of care clinic assessments such as bilateral muscle strength and stability screening will be performed in all patients at 8 and 12 weeks of rehabilitation. Time to return to sport for those subjects participating in a recreational or professional sport activities will also be recorded. Lastly, quadriceps muscle mass measured through dual energy x-ray absorptiometry (DEXA) scanning. Participants in all 3 groups will undergo DEXA scanning at once pre-operatively, 4 weeks post-op,8 weeks, post-op and 12 weeks post-op following ACL reconstruction.

The Tampa Scale and KOOS JR surveys will be administered at each study visit. The purpose of these surveys are to evaluate patient perception of surgery and their injury. As stated in the purpose, these will act as secondary outcomes to this study.

Inclusion Criteria:

• Subjects will include patients age 16 to 40 undergoing primary ACL reconstruction for an acute ACL tear with the PI or Sub-investigators

Exclusion Criteria:

• Subjects will not be included if they meet one of the following criteria

  • History of meniscectomy or meniscus repair

  • Obesity (BMI>35)

  • Diabetes

  • Cardiovascular, renal, liver or pulmonary disease

  • Active infections

  • Cancer (current or treated within the past 2 years) or coagulation disorder

  • Rapid weight change within the past year

  • Physically unable to participate in the intervention

  • Are currently taking, or recently (w/in 1 month of participation) taken prescribed, or over the counter ergogenic aids or compounds known to be banned by the NCAA.

  • Less than 16 years of age

  • Vegan patients

  • Patient over the age of 40

  • Pregnancy ( As part of standard of care, all female participants will be administered a urine pregnancy test prior to surgery. A negative test result is required to participate in the study.)

  • Any known or diagnosed kidney, GI, or liver disorders

  • Taking any medications known to affect protein metabolism. This includes, but is not limited to any drugs involved in hormone replacement therapy to treat conditions such as:

    • Hypothyroidism: example - levothyroxine
    • Hypogonadism: example - exogenous testosterone, estrogen, or any other forms of androgenic or anabolic hormone compounds
    • Growth hormone or growth hormone analogues
    • Type I or Type II diabetes requiring insulin

  • Currently taking protein supplements, amino acid supplements, or any known ergogenic aids.

  • Notably, all patients would need to confirm they will be doing their rehab through Houston Methodist

  • Patients diagnosed with protein intolerance or digestive issues associated with consuming protein

This is a double-blinded randomized controlled trial.