Essential Amino Acid Supplementation Mitigates Muscle Atrophy After Total Knee Arthroplasty: A Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND: Substantial muscle atrophy occurs after total knee arthroplasty (TKA), resulting in decreased strength and impaired mobility. We sought to determine whether perioperative supplementation with essential amino acids (EAA) would attenuate muscle atrophy following TKA and whether the supplements were safe for ingestion in an older surgical population. METHODS: We performed a double-blind, placebo-controlled, randomized trial of 39 adults (age range, 53 to 76 years) undergoing primary unilateral TKA who ingested 20 g of EAA (n = 19) or placebo (n = 20) twice daily for 7 days preoperatively and for 6 weeks postoperatively. At baseline and 6 weeks postoperatively, magnetic resonance imaging (MRI) scans were obtained to measure quadriceps and hamstrings muscle volume. Secondary outcomes included functional mobility and strength. Data on physical activity, diet, and patient-reported outcomes (Veterans RAND 12-Item Health Survey and Knee injury and Osteoarthritis Outcome Score) were collected. Safety was determined through blood tests evaluating blood urea nitrogen, creatinine, creatinine clearance, homocysteine, and renal and liver function. Laboratory values at baseline, on the day of surgery, and at 2 days, 2 weeks, and 6 weeks postoperatively were compared between treatment groups. Analysis of covariance models, with baseline values as covariates, were used to evaluate outcomes between treatment groups. P values were adjusted for multiple tests. RESULTS: Compared with baseline, the EAA group had significantly less decrease in mean quadriceps muscle volume compared with the placebo group in the involved leg (−8.5% ± 2.5% compared with −13.4% ± 1.9%; p = 0.033) and the contralateral leg (−1.5% ± 1.6% compared with −7.2% ± 1.4%; p = 0.014). The hamstrings also demonstrated a greater muscle-volume-sparing effect for the EAA group than for the placebo group in the involved leg (−7.4% ± 2.0% compared with −12.2% ± 1.4%; p = 0.036) and contralateral leg (−2.1% ± 1.3% compared with −7.5% ± 1.5%; p = 0.005). There were no differences between the groups in terms of functional measures or strength. Blood chemistry values varied significantly between assessments periods but did not statistically differ between groups. CONCLUSIONS: The results of the present study suggest that EAA supplementation is safe and reduces the loss of muscle volume in older adults recovering from TKA. LEVEL OF EVIDENCE: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.