Wearable technology is generally interpreted as electronic devices with passive and/or active electronic components worn on the human body. A further sub-set of wearable technology includes devices that are equipped with sensing abilities for body movements or biosignals and computational power that allows for further analysis. Wearable devices can be distinguished by different levels of wearability: wearable devices integrated into clothing, which are an integral part of the clothes; and wearable devices put on as an accessory. This thesis introduces a novel approach to truly wearable sensing of body movement through novel garment-integrated sensors. It starts from an initial investigation of garment movement in order to quantify the effect that garment movement has on sensor accuracy in garment-integrated sensors; continues with the development and detailed characterization of garment-integrated sensors that use a stitched technique to create comfortable, soft sensors capable of sensing stretch and bend; and ends with a final evaluation of the proposed wearable solution for the specific case of knee joint monitoring in both the stretch and bend modalities.