The purpose of this dissertation work was to investigate how fear of movement (kinesiophobia) impacts physical activity in adults with knee OA, in combination with osteoarthritis (OA) related physical, biomechanical, and functional impairments. The first study investigated the relationships between muscle strength and physical activity level and determined whether this association is mediated by kinesiophobia and pain. Lower knee flexion and extension strength were associated with lower physical activity and these relationships were mediated by higher kinesiophobia (more fear) but not pain.

The second investigation determined the relationship between walking gait parameters and physical activity and explored whether kinesiophobia contributes to these relationships. In this study female sex, a slower self-selected walking speed, and higher kinesiophobia significantly contributed to explaining lower physical activity level.

The final study investigated the effects of selected performance-based physical function measures in explaining physical activity and determined whether kinesiophobia may contribute to activity beyond what is explained by these functional measures. Better performance on all physical function measures and less fear of movement were significant predictors of higher physical activity level even after accounting for sex. Further, there was a significant increase in predictive power when kinesiophobia was accounted for, although the functional tests demonstrated the highest predictive power.

The three studies discussed in this dissertation work address the importance of accounting for psychological factors, specifically fear of movement (kinesiophobia), when assessing OA-related impairments and limitations related to physical activity in adults with OA. The findings are exploratory in nature but contribute to the understanding of how behavioral adaptions due to OA-related impairments can have a global effect on the body and in turn impact physical activity level.