Effects of Essential Amino Acid Supplementation on Clinical Outcomes in the Conservative Management of Knee Osteoarthritis.

BACKGROUND

The effect of supplementation of essential amino acids (EAAs) in knee osteoarthritis (OA) remains unclear. This study aimed to evaluate whether supplementation with EAA improves pain, patient-reported outcome measures, gait function, and quadriceps muscle volume in patients undergoing conservative treatment for knee OA.

METHODS

A retrospective cohort study was conducted on outpatients undergoing physical therapy from April 2024 to March 2025. Inclusion criteria were patients who started physical therapy for knee OA, with exclusion of patients taking other supplements or having severe medical conditions. Patients who received EAA at the beginning of physical therapy were assigned to the EAA group (8 g/day supplementation), while those who did not were assigned to the control group. The primary outcome was the maximum value on the visual analogue scale (VAS). Secondary outcomes included the Knee injury and Osteoarthritis Outcome Score (KOOS) subscales, gait speed and steps, quadriceps torque, and quadriceps volume measured at baseline and 12 weeks.

RESULTS

Of the 51 patients initially included, 36 patients were ultimately analyzed (EAA group: n = 17, control group: n = 19). No significant differences were observed in VAS, KOOS subscales, and quadriceps torque between groups. However, the EAA group demonstrated significantly greater improvements in 6-meter gait speed, step count, and quadriceps volume compared to the control group. No adverse effects were observed associated with EAA supplementation.

CONCLUSIONS

EAA supplementation in the conservative treatment of knee OA demonstrated significant improvements in gait function and quadriceps muscle volume compared to the control group. These results suggest the efficacy of EAA supplementation in the conservative management of knee OA.