• Physical functioning as measured with the Western Ontario and McMasters osteoarthritis index
  

• Leg-specific pain and stiffness as measured with the WOMAC
  
• The Lequesne Knee Score
  
• The physical component summary of the SF-36
  
• EuroQoL-5D
  
• Patient satisfaction
  
• Balance abilities as investigated with the Biodex Stability System®
  
• Motoric coordination as assessed by a shortened version of the “Dortmunder modified Romberg Test for Seniors”
  
• Proprioception assessed according to guidelines established by Barrack and Swanik
  
• Axis relations evaluated by postoperative standardized lateral and AP X-rays
  

Various risk factors influencing the success of Total Knee Arthroplasty (TKA) have been studied.

Today age, gender, primary or revision surgery, comorbidities and baseline characteristics are known to influence the health-related quality of life after TKA. It is thought, that accurate mechanical alignment and ligament balance ensure optimal kinematic performance and wear, which in turn improves long-term outcome. During preparation of the bone for the implantation of the knee prosthesis, numerous cuts are performed. Traditionally mechanical adjusted jigs are used to accurately align and position the instruments. Since this alignment process is a source for deviation even in experienced surgeons, several navigation systems were developed. Using these systems, the surgeon is guided in the location of the instruments with the help of a computer.

Several studies could show that the use of such a navigation system leads to an improved execution of planned axis relations, as measured on the radiographs. However, it is not clear, whether or to what extent the improved realization of the preoperative planned axis relations results in a positive effect for the patient. This multicenter randomized clinical trail is conducted to compare the operative results of navigated and non-navigated knee replacement surgery.

The aim of this study is to evaluate the use of a navigation system on health-related quality of life, measured as pain, stiffness, physical function, coordinative abilities, and patient satisfaction. The hypotheses tested is that the use of the navigation system for total knee arthroplasty leads to improved health-related quality of life.