The Oxford Knee Score is a reliable 12-item, patient-reported questionnaire originally developed and validated specifically to assess function and pain in patients undergoing total knee replacement. It is short, reproducible, valid and sensitive to clinically important changes over time. Each of the 12 questions on the OKS is scored in the same way with the score decreasing as the reported symptoms increase (i.e. become worse). All questions are laid out with response categories denoting least (or no) symptoms to the left of the page (scoring 4) and those representing greatest severity lying on the right hand side (scoring 0), as detailed for question 1 below. This method, when summed, produces overall scores running from 0 to 48 with 48 being the best outcome, (to convert from the 60-12 system to the 0-48 system and vice versa subtract the score from 60).

EQ-5D is a standardized 5-dimension 5-level measure of the health status and is developed by the EuroQol Group in order to have a simple and generic measure for clinical and economic assessment. Instructions for the user are directly included into the questionnaire and it consists of two pages. One cover five different dimensions (mobility, self care, usual activities, pain/discomfort, anxiety/depression) and the other one the EQ visual Analogue Scale (EQ-VAS). The VAS scale records the self rated health status of the patient from the level "the worst health you can imagine" to "the best health you can imagine".

Imaging will be used to evaluate the implant status as well as device condition and potential presence of device-related Adverse Events including fracture, wear, loosening or radiolucencies.

Alignment (femoral-knee baseline angle, tibial-knee baseline angle, femoral-tibial angle (mechanical))

Available retrievals of explanted investigational products will be analysed by the biomechanical laboratory of the sponsor. Therefore any retrieval has to be returned to the Sponsor's facility after its revision in order to perform these analyses. Special focus of theses analyses are the oxidation profile, the wear behaviour, the mechanics and the cumulative linear abrasion of these retrievals. These measurements can further analyse the in-vivo performance of the device of the reference and investigational product

In case a patient requires the revision of the primary implanted knee prosthesis, additional information on the revision surgery shall be collected. The reason for revision together with the clinical symptoms shall be documented. Further examinations (e.g. arthroscopy) prior to the revision and the date of revision surgery is to be documented. If pre revision radiographs are taken as part of the clinical routine, the results of the radiographic analysis shall be documented in the respective CRF.

During the course of the study, any upcoming intra- or postoperative (serious) adverse device events or effects related or not related to the product under investigation, will be documented. The total number of AEs will be summarized and further evaluated by the sponsor and reported according to local legislation and necessity. Recorded complications will be categorized and analyzed in order to assess the safety of the investigational product.