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Combined findings from two long term studies indicate an association between a fibre-rich diet and a lower risk of painful knee osteoarthritis (OA). Dietary fibre is known to reduce body weight and inflammation, both of which are linked with knee OA. Researchers from Tufts University in Massachusetts mined data from two US studies to determine whether dietary fibre modifies the risks of x-ray evidence of knee OA, symptomatic knee OA (x-ray evidence and symptoms, such as pain and stiffness), and worsening knee pain. Data were taken from the Osteoarthritis Initiative (OAI; 4796 participants) and the Framingham Offspring Osteoarthritis Study (1268 participants). In both studies, dietary fibre intake was assessed at baseline with the Food Frequency Questionnaire. Information on symptoms and x-ray evidence were collected annually for 4 years (OAI) or assessed after 9 years (Framingham). Data were also gathered on potentially relevant factors, such as knee injury or surgery, medication and lifestyle, including tobacco and alcohol use and physical exercise. Of the 4051 participants in the OAI with complete data on dietary fibre intake, 869 knees were symptomatic, 152 had x-ray evidence of OA, and pain had worsened in 1964 after 4 years. In the Framingham study, of 971 participants with complete dietary fibre data, 143 knees were symptomatic and 175 displayed x-ray evidence of OA after an average 9 years. Patients with the lowest fibre intake (bottom 25% of participants) had a 30% lower risk of painful knee OA than those with the highest fibre intake (top 25%) in the OAI, and a 61% lower risk in the Framingham study. But fibre intake did not affect x-ray evidence of knee OA. In addition, the OAI found that eating more fibre in general and a high cereal fibre intake were each associated with a significantly lower risk of worsening knee pain. This was an observational study, so no firm conclusions can be drawn about cause and effect. The findings were published in the Annals of the Rheumatic Diseases.