Identification of barriers and levers to regular physical activity using the EPAP questionnaire. This questionnaire contains 24 items on the facilities and obstacles encountered when engaging in physical activity. The maximum score for this questionnaire is 100 points. Responses range from "Strongly disagree" (0 points) to "Strongly agree" (4 points). Responses to this questionnaire will be collected at inclusion and at the end of the study.

Evaluation of fears and anxieties related to pain that may be experienced during physical exercise using the TSK questionnaire at inclusion and at the end of the study. This questionnaire contains 17 statements. Patients were asked to circle the number that best corresponded to them (4 points). Responses ranged from "Strongly disagree" (1 point) to "Strongly agree" (4 points). The maximum score is 68. The higher the score, the greater the level of kinesiophobia.

Comparison of the functional evaluation collected at inclusion and at 6 months of use of the application via the Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaire. This questionnaire consists of 17 statements answering the question "Over the last eight days, how difficult́ have you beeń doing each of the following activities?". Responses range from "absent" (0 points) to "extreme" (4 points). The maximum score is 68. A high score is predictive of functional deterioration.

Evaluation of quality of life using the EQ-5D-3L questionnaire. This questionnaire consists of two aspects: a descriptive system (EQ-5D) and a visual analogue scale (EQ-VAS). The questionnaire comprises five dimensions: mobility, personal care, usual activities, pain/discomfort and anxiety/depression. Each dimension has 3 levels: no problems, a few problems and extreme problems. The patient therefore ticks the box that seems most appropriate to their current state.

Measurement of joint mobility with a goniometer (flexion/extension)

Collection of average number of steps per day for 6 months during telephone calls (every 2 months). The GARMIN connected bracelet will allow us to collect the number of average steps per day (four measurement times over one week before each evaluation: inclusion, 2 months, 4 months and 6 months) via its GARMIN connect application.

Collection of parameters for use of the ARTHE application, if applicable (for the intervention group), the number of sessions carried out per week will be collected by extracting data from the application's production back office.

Functional tests: number of 30-second chair lifts at inclusion and at 6 months.The patient should remain in the sit-to-stand position for as long as possible (30 sec). The evaluator counts the number of sit-ups performed.

Functional tests: Stair Climbing Test (in seconds) at inclusion and at 6 months. The patient will be asked to climb 1The patient will be asked to climb 11 steps (height 13.5cm), make a U-turn and descend them as quickly as possible, while maintaining safety during the test (no loss of balance). Climbing and descending time will be measured separately with a stopwatch. 1 steps (height 13.5cm), make a half-turn and descend them as quickly as possible, but keeping safe during the test (without loss of balance). Climbing and descending times will be measured separately with a stopwatch.

Functional tests: 6-minute walk test (6 MWT) (in meters) at inclusion and at 6 months.This test carried out in a corridor with pads numbered from 1 to 60. The patient must walk back and forth for 6 minutes. The examiner measures the distance covered during these 6 minutes.

Functional tests: quadriceps isometric strength test (in N/Kg)with a dynamometer at inclusion and at 6 months. The participant will be asked to push the leg forward as hard as possible (isometric contraction of the quadriceps) for 5 seconds. Three trial contractions will be performed with progressive effort (weak, medium and strong). Then, three consecutive maximum contractions will be recorded using a dynamometer. The maximum value will be recorded and normalized in relation to the patient's body mass [N/kg].

Medico-economic analysis carried out using a data record (drug management, medical consultations, hospitalisations, use of alternative therapies, additional examinations, use of medical transport).

Change in the average level of pain over the last 3 days collected during the telephone interview using a 10-point Numerical Scale (0 = "No pain" to 10 = "Maximum imaginable pain") at inclusion, 2 months, 4 months and 6 months of use of the application.