Background
age-related disease, pain
OSTEOARTHRITIS OF THE KNEE
Osteoarthritis of the knee (OAK) is a highly prevalent, progressive, age-related disease that causes pain and stiffness of the affected joint, causing reductions in individuals’ quality of life [Although patients with OAK report strong intentions to adapt their lifestyles to relieve severity or slow progression of OAK symptoms [The HAPA also considers contextual barriers (e.g., environmental conditions such as rainy weather) and facilitators to behavior change [There has been extensive research on PA in patients with OAK, however, only few intervention programs were theory-based [Furthermore, most HAPA-based interventions so far have addressed contextual facilitators or barriers indirectly, for instance, as part of action or coping planning strategies where participants identify (alone or with others) good opportunities to act or barriers that keep them from implementing the planned behavior [In addition, current RCTs with patients with OAK mainly focus on shorter-term effects [