Krill Oil for Knee Osteoarthritis: A Randomized Clinical Trial

Laslett LL, Scheepers LEJM, Antony B, et al. · JAMA

Krill oil did not improve knee pain versus placebo (VAS change -19.9 vs -20.2; difference -0.3, 95% CI -6.9 to 6.4, p = 0.94). An adequately powered null in participants recruited for an inflammatory phenotype, and WOMAC pain, function, hand pain and back pain were null alongside it. Of the trial's sixty secondary outcomes one separated, and it went the other way: effusion-synovitis volume — the inflammation people were recruited on — rose 0.81 mL on krill oil and fell 0.94 mL on placebo, a difference of 1.75 mL favouring placebo (95% CI 0.37 to 3.13, p = 0.01). The authors call it unexpected and say it may be chance at that number of outcomes. The Omega-3 Index rose from 6.5% to 8.0% on krill oil and stayed flat on placebo, so the capsules were taken.

Population

Adults with clinical knee OA, significant pain, and effusion-synovitis on MRI; 5 Australian centres, 24 weeks

Intervention

2 g/day krill oil (EPA+DHA source)

Comparator

Placebo

Limitations

24 weeks may be short for structural effects, and the authors' own first limitation is that 2 g/day may simply be too little: it delivers 380 mg EPA and 200 mg DHA against the 600 and 280 of the positive 2022 trial, and reached an Omega-3 Index of 8.0% against that trial's 9.0%. They also note their participants started higher (6.5% against 5.7%) and, unlike that trial, were not required to keep dietary omega-3 under 500 mg/day — which is the repletion reading. MRI was without contrast, so effusion and synovitis could not be told apart, and the findings do not extend to knees without an effusion. Funded by the NHMRC and the University of Tasmania; Aker Biomarine supplied the krill oil and placebo softgels and processed the blood for the Omega-3 Index.