The KROMM, “Knee Range of Motion Monitoring” is a knee wearable electrogoniometer composed of a knee angular sensor and a three-axis accelerometer placed on the thigh. The clinical relevance of this device is guarantee to the clinicians the possibility of an accurate assessment of the knee range of motion during walking and stair ambulation and to the patients with knee osteoarthritis a personalized rehabilitation also in the home setting. The aim of this stage of the study is developing the next version of the KROMM system achieving three main goals: 1.improving the activity detection capability of the algorithm incorporated into the sensors; 2.improving the ergonomics of the design for avoid sudden breaks and uncomfortable usability; 3.improving the user- friendliness of the app on the smartphone for help the patients in the home environment giving information about the time spent in each activity.