Krill oil improved osteoarthritic knee pain in adults with mild to moderate knee osteoarthritis: a 6-month multicenter, randomized, double-blind, placebo-controlled trial

BACKGROUND: Osteoarthritis (OA) is a major cause of chronic pain and disability worldwide. Treatment generally focuses on symptom relief through nonsteroidal anti-inflammatory drugs (NSAIDs) and analgesics, which may incur side effects. Krill oil, rich in anti-inflammatory long-chain (LC) omega-3 ( ω–3) PUFAs and astaxanthin, may be a safe and effective alternative treatment. OBJECTIVES: This study sought to investigate the effects of a commercially available krill oil supplement on knee pain in adults with mild to moderate knee OA. Secondary outcomes were knee stiffness; physical function; NSAID use; Omega-3 Index; and lipid, inflammatory, and safety markers. METHODS: Healthy adults (n = 235, 40–65 y old, BMI >18.5 to <35 kg/m(2)), clinically diagnosed with mild to moderate knee OA, regular knee pain, and consuming <0.5 g/d LC ω-3 PUFAs, participated in a 6-mo double-blind, randomized, placebo-controlled, multicenter trial. Participants consumed either 4 g krill oil/d (0.60 g EPA/d, 0.28 g DHA/d, 0.45 mg astaxanthin/d) or placebo (mixed vegetable oil). Knee outcomes were assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) numeric scale (normalized to scores of 0–100). Outcomes were assessed at baseline, 3 mo, and 6 mo. RESULTS: Omega-3 Index increased with the krill oil supplement compared with placebo (from 6.0% to 8.9% compared with from 5.5% to 5.4%, P < 0.001). Knee pain score improved in both groups with greater improvements for krill oil than for placebo (difference in adjusted mean change between groups at 6 mo: −5.18; 95% CI: −10.0, −0.32; P = 0.04). Knee stiffness and physical function also had greater improvements with krill oil than with placebo (difference in adjusted mean change between groups at 6 mo: −6.45; 95% CI: −12.1, −0.9 and −4.67; 95% CI: −9.26, −0.05, respectively; P < 0.05). NSAID use, serum lipids, and inflammatory and safety markers did not differ between groups. CONCLUSIONS: Krill oil was safe to consume and resulted in modest improvements in knee pain, stiffness, and physical function in adults with mild to moderate knee OA. This trial was registered at clinicaltrials.gov as NCT03483090.