To date, treatment options for knee osteoarthritis remain limited, and their clinical evaluation is complex due to the day-to-day fluctuations in symptoms. Hospital tests provide a point-in-time measurement that is influenced by various factors (fatigue, recent activity, weather, etc.), making reliable assessment difficult. The aim of the study is to assess the feasibility and acceptability of monitoring actual activity using the Syde® portable device in up to 30 subjects. Numerical variables derived from data collected by Syde® will be compared with conventional on-site clinical assessment criteria and with data from healthy participants, in order to identify a reliable and robust metric, thereby improving treatment evaluation and personalised patient management. MAIN OBJECTIVES * Evaluate the use of the device * Identify numerical variables and determine the optimal time window for evaluation Patients will have two visits: one at inclusion and a second two months later. They will wear Syde® magneto-inertial sensors, one on each ankle, for the month following the initial visit, then a Syde® sensor on the ankle and another on the wrist on the side of the non-dominant hand for the following month. The total duration of the recording period is two months.