Knee Osteoarthritis: A Clinical Trial Examining Therapeutic Effects of High-Rosmarinic Acid Spearmint Tea and Investigations into Relationships of Pain With Modifiable Lifestyle Factors and Biomarkers of Joint Metabolism and Inflammation

Osteoarthritis (OA) is a chronic, progressive disease involving the degeneration of cartilage and joint tissue, resulting in pain and disability. This thesis investigated OA knee pain and physical function, namely associations with lifestyle factors and biomarkers as well as a novel therapeutic product to manage symptoms of knee OA. In a survey of healthy adults with knee OA (n=197), OA characteristics, health history and information about smoking history, alcohol consumption, height, body weight, medication and supplement intake, and exercise habits were collected. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was used to assess pain. OA medication use and higher body mass index (BMI) category were associated with higher pain. Supplement use and meeting physical activity guidelines (150 min/week) were associated with lower pain. Next, associations between OA symptoms and biomarkers of joint metabolism and inflammation (n=54) were analyzed using Spearman correlation coefficients, controlling for age, gender and BMI. Serum hyaluronic acid was significantly associated with better performance in the 6-minute walk test (6MWT) and stair climb test (SCT). Serum matrix mellatoproteinase-3 was significantly associated with higher pain. Interleukin-6 was significantly associated with higher pain, stiffness and worse performance in the SCT. Finally, in a randomized, double-blind clinical trial, participants (n=46) consumed tea brewed from a high-rosmarinic acid (rosA) spearmint or a commercially available spearmint twice daily for 16 weeks. Pain significantly decreased within the high-rosA group, but not the control group and scores for stiffness and physical disability significantly decreased within both groups. Increased quality of life score on the bodily pain index in the short form (SF)-36 questionnaire was observed within the high-rosA group only. In the 6MWT, only the high-rosA group increased distance walked at Week 16, but the increase was not statistically significant. There were no changes in the SCT within either group. Overall, this thesis found associations between OA symptoms and biomarkers of joint metabolism and inflammation and characterized the relationship between OA pain and certain lifestyle factors. Also, for the first time, a decrease in pain with consumption of a high-rosA acid spearmint tea was observed, rationalizing further consideration in the management of knee OA pain.