Abstract
The relevance of physical activity (PA) for general health and the value of assessing PA in the free-living environment especially for assessing orthopaedic conditions and outcome are discussed. Available methods for assessing PA such as self-reports, trackers, phone apps and clinical grade monitors are introduced. An overview of devices such as accelerometers for research quality assessments is given and aspects for choosing them such as wear location, usability or study population are reviewed. Basic principles to derive mobility parameters from the PA related sensor signals are presented. The symposium explains mobility parameters, their types, definitions, validity, analysis and those with particular relevance to assess orthopaedic conditions. The application of activity monitors is orthopaedic patient studies is demonstrated in various examples such as knee and hop osteoarthritis and total joint arthroplasty, in frail elderly subjects at fall risk or patients with shoulder pathologies.