||Mobile monitoring of health-related parameters is a hype and can be very useful for healthcare practitioners and researchers to evaluate the efficacy of patients' treatment programs. Several cell phone applications are available to track activity parameters like heart rate, number of steps and hours of activity and rest. Their use for monitoring orthopaedic disorders of the lower limb has not yet been introduced and validated in clinical practice. However, it can be highly relevant for health care practitioners to monitor the functional outcomes in patients with musculoskeletal disorders. Mechanical loading is a contributing factor to the onset and progression of degenerative joint disease and artificial implant wear. Therefore, mobile monitoring of the evolution of a patient's total loading profile, i.e. his functional state based on an extended analysis of the activity profile, seems feasible, relevant and conceptually within reach. In this project, an integrated mobile application will be designed for monitoring and managing the loading profile in subjects with degenerative hip and knee problems prior and after surgical intervention.