Objectives　A randomized, double-blind, placebo-controlled trial was conducted to investigate the effects of Krill oil on quality of life（QOL）in healthy subjects with mild knee pain.
Methods　Eighty-one Japanese adults with complaints of mild knee pain were enrolled by a physician into this study. Subjects were randomly assigned to one of three groups. Participants in the KO-500（n＝27）group ingested 500 mg/day of Krill oil. Participants in the KO-1000（n＝26）group ingested 1000 mg/day of Krill oil. The remaining participants（n＝27）received a daily placebo containing no Krill oil. Participants ingested four capsules（containing either Krill oil or placebo）per day for 4 weeks. The mild knee pain related to QOL was measured by administration of the Japanese Knee Osteoarthritis Measure（JKOM）, the Knee Function Score assessed by Japanese Orthopaedic Association（JOA）, and high-sensitivity C-reactive protein（hs-CRP）at baseline and after 4 weeks of Krill oil or placebo. Physical examination, urinalysis, and blood tests were used to assess safety of the treatments.
Results　One subject in KO-1000 group was excluded due to noncompliance. The final analysis included 27, 26, and 27 participants from the KO-500 group, KO-1000 group, and placebo group, respectively. Hs-CRP level was significantly lower in the KO-500 group than in the placebo group at 4 weeks following treatment initiation（P＝0.034）. JKOM and JOA scores did not significantly improve or differ among groups. A four-week period of consumption of Krill oil was determined to be safe under the conditions of this study.
Conclusions　The result suggested that Krill oil may relieve the knee joint inflammation and improve knee-related QOL in healthy Japanese adults with mild knee pain. Krill oil was also safe under the conditions of this study.