One hundred twenty adults aged 55–80 years with early signs of knee osteoarthritis were randomized to receive either 3 g/day of GreenShell mussel powder (PERNAULTRA) (n=61) or placebo (pea protein) (n=59) for six months. The primary outcome was improvement in physical performance measures, including the 30-second chair stand, stair test, and 40-m fast-paced walk. Secondary outcomes included changes in the Knee Injury and Osteoarthritis Outcome Score (KOOS), Intermittent and Constant Osteoarthritis Pain (ICOAP) scores, and visual analog scale (VAS) for pain and symptoms. Outcomes were assessed at baseline and after six months. Overall, the results revealed a significant improvement in VAS symptoms for the GSM group compared to placebo and trends for improvement in walking speed and symptom subscales. In participants with BMI <25, GSM also significantly improved KOOS-S (P=0.03). These findings suggest that whole powdered GSM may alleviate symptoms and modestly improve function in adults with early knee osteoarthritis.