disease by pre-specified questions, and those over 60 years of age had electrocardiogram monitoring during the test. Pain level the last week was measured by a numeric rating scale (0-10, 0¼no pain). The VO 2max data were compared to normative data assessed by treadmill tests in two Norwegian cohort studies: 1) the population-based study of objectively measured physical activity in Norway (KAN2) (n¼777), and 2) the Health in Nord-Trøndelag Study (HUNT3 fitness)(n¼4631); the largest European reference material of objectively measured aerobic fitness in healthy men and women aged 20-90 years. Data were divided into age and sex groups. One sample t-test or Wilcoxon one sample signed rank test were used for the group comparisons of VO 2max. The association between VO 2max and pain was analyzed using linear regression model, adjusted for age, sex and educational level. Results: The mean age of men and women were 56.4 (7.5) years and 56.5 (6.8) years, respectively. The mean BMI of men and women were 29.2 (3.4) and 27.3(3.5), respectively, and significantly lower than the KAN2 study (men 26.3(3.4) and women 27.3 (23.0-37.4) and the HUNT3 fitness study [men 26.6 (3.2) and women 25.4 (3.9)]. The meanVO 2max for men were 31.5(5.7) and for women 24.9 (4.4) mL•kg-1 •min-1. The men had between 17.2% and 13.4% lower VO 2max than in KAN2 for the corresponding age groups (p<0.05) and they had between 23.8% and 26.4% lower VO 2max than in HUNT3 fitness (p<0.05)(Table).The women had between 16.0% and 15.5% lower VO 2max than in KAN2 (p<0.05), and between 25.2% and 19.2% lower VO 2max than in HUNT3 fitness (p<0.05)(Table). There was a statistically significant association between VO 2max and pain in the adjusted analysis (b¼-0.63 mL•kg-1 •min-1 95% CI:-1.23,-0.04, p¼0.036) with R 2 of 0.51. Conclusions: Patients with knee osteoarthritis had considerably lower levels of physical fitness than healthy individuals, however, the study should be repeated with a larger sample size. Knee pain, age, BMI and educational level explained 51% of the variation in physical fitness. Clinicians should communicate clearly that physical activity does not increase severity of knee osteoarthritis and help find activities to increase physical fitness in individuals with knee osteoarthritis.

The research was undertaken with funding support from the RCSI undergraduate summer student research programme.