Chronic knee joint pain is common in the elderly and associated with poor quality of life. This study, an open-label clinical trial, aimed to examine how the intake on a daily basis of maslinic acid-containing product (30 mg maslinic acid) on 29 elderly residents (mean 70.7 ± 10.1 years) of Nakajima Island, Ehime, Japan. Study participants consumed 10 g jelly containing maslinic acid daily for 16 weeks and at 0 (baseline), 4, 8, 12 and 16 weeks, assessed for health-related quality of life (Short Form-8) and knee pain score (Japanese Knee Osteoarthritis Measure). After 16 weeks, the physical quality of life, more specifically, the level of Bodily Pain and Physical Component Summary, but not mental quality of life, was significantly improved by maslinic acid intake. Furthermore, maslinic acid intake significantly decreased the Japanese Knee Osteoarthritis Measure at week 8 and tended to decrease Visual Analogue Scale score at weeks 4 and 16. These results suggest that consumption of maslinic acid has a protective effect against chronic knee pain in elderly residents in a community where knee pain causes high quality of life burden.