The goal of this proposed study is to examine the effects of dietary wild blueberries on gut microbiome, serum markers of inflammation, and joint function in adults. Each participant will consume 25g freeze-dried blueberries or matched placebo powder for 12 weeks, with a 2-week washout phase between.

Inclusion Criteria:

• Adults with documented multi-joint/knee arthritis

Exclusion Criteria:

• inability to give informed consent
• pregnancy or lactation
• planned knee replacement surgery
• allergy or contraindication to berries
• recent trauma of the knee responsible of the symptomatic knee
• intra-articular injection in the target knee/hip in the last 3 months
• oral corticosteroid therapy ≥ 5 mg/day (prednisone equivalent) at baseline
• use of berry extracts in the last 3 months
• special diets
• cancer treatment
• bone diseases