This multicenter, prospective, randomized controlled trial evaluates whether postoperative administration of branched chain amino acids affects skeletal muscle mass index and sarcopenia related functional outcomes in patients undergoing total knee arthroplasty.

Participants are randomly assigned to receive Livact granules 4.15 g three times daily for 3 months after surgery or to receive standard postoperative care without branched chain amino acid administration. Skeletal muscle mass index, physical function, patient reported outcomes, laboratory findings, medication compliance, and adverse events are assessed at baseline, 5 weeks, and 15 weeks after surgery.

Inclusion Criteria:

1. Patients aged 40 to 100 years who are scheduled to undergo total knee arthroplasty.

Exclusion Criteria:

1. Participants who used antiretroviral agents within 4 weeks before the first administration of Livact.
2. Participants who used medications associated with fatty liver within 4 weeks before the first administration of Livact, including thiazolidinediones, sodium glucose cotransporter 2 inhibitors, amiodarone, methotrexate, tamoxifen, valproate, or corticosteroids.
3. Participants who used branched chain amino acid products or multinutritional supplements within 4 weeks before the first administration of Livact.
4. Participants who used pain medications other than those prescribed for total knee arthroplasty treatment within 2 weeks before the first administration of Livact.
5. Participants with markedly decreased hepatic protein synthetic function.
6. Participants with congenital branched chain amino acid metabolism disorders.
7. Participants with hereditary galactose intolerance, Lapp lactase deficiency, or glucose galactose malabsorption.
8. Participants with a history of high tibial osteotomy.
9. Participants with neurologic diseases such as stroke or Parkinson disease.
10. Participants with gait disturbance due to causes other than arthritis.
11. Participants taking medication for spinal stenosis.
12. Participants with a history of hypersensitivity to the investigational product or its components.
13. Pregnant or breastfeeding participants.
14. Participants planning pregnancy during the trial or who have the possibility of pregnancy but do not agree to use appropriate contraception during the trial.
15. Participants judged by the investigator to be inappropriate for participation in the clinical trial.

Individual participant data will not be shared because the data contain sensitive clinical information and are subject to institutional review board approval, hospital data protection requirements, and participant confidentiality obligations.