Sports or physical exercises are known to have a positive effect on chronic diseases such as obesity, diabetes, heart disease, depression, and osteoarthritis. In the prevention and rehabilitation of these chronic diseases it is important that the patient regularly and correctly performs specific exercises, as prescribed by a therapist. Therefore, it is important that the therapist knows whether the patient performs the exercises at home (adherence), and in which way he performs them (quality). At present, the only way to measure human movement is by means of a three-dimensional motion capture system (Coda Motion, Vicon) combined with a pressure distribution plate and force platform. This equipment is expensive and not widely available and can be only used in specialized laboratories. Furthermore, it has been attempted to develop simple measuring devices that are portable but they all have their limitations. Pedometers do not perform well with abnormal gait patterns or are not sensitive enough to distinguish between certain activities (e.g. ascending, descending stairs). In dynamic and complex conditions, accelerometers have the disadvantage of being inaccurate. By adding a gyroscope and magnetometer the complexity will quickly increase and ask a lot of energy which is detrimental for long-term monitoring. Angular measurement devices, called electro goniometers, consist of strain gauges, inductive measuring wires (disadvantage: high risk of wire breakage), optical measuring wires (disadvantage: transmitter - receiver and has relatively high power requirement). Because all of these technologies have their specific drawbacks, there is actually no ready measuring principle that can be used for long-term ambulatory monitoring of physical activities. MoTex is a multidisciplinary project with the objective to implement technology in the therapy / rehabilitation process. In this context we will develop a principle to accurately measure knee angles (both flexion/extension and valgus/vagus). The selected sensor technology must be easy to use so that the patient is able to equip himself without any help. The technology may not have any functional effects on the exercise or on movements to be performed. Initially we focus on the knee joint and therefore we want to develop a "Smart Textile" that can be integrated into a "Body Area Network". To improve the efficiency of the platform the device will be tested in two different cases. Firstly, we will focus on the prevention and recovery of functional knee instability and secondly we will focus on the monitoring of the therapy in the rehabilitation of knee osteoarthritis.