• 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

This study is undertaken to investigate the effect of navigated knee implantation surgery on physical function, joint stiffness, pain, quality of life and coordinative abilities.

One group of patients will receive navigated knee implantation surgery, the other traditional knee implantation surgery, without use of the navigation system.

The study is designed as a randomized trial. That means that all patients who have given their consent to participate in this study will be allocated to either navigated or conventional surgery by chance.

A total of 477 patients will be included in this study and will be followed up for 12 month.

In this period all patients will be asked to fill in functional and quality of life questionnaires at baseline, 6 weeks and 3, 6 and 12 month follow-up. Coordinative abilities will be evaluated once in the time-frame 3 to 6 months postoperatively.

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.

Inclusion Criteria:

• All patients who are scheduled to receive a Total Knee Arthroplasty at the participating institutions for primary diagnosis of osteoarthritis are candidates for inclusion in the study.

Exclusion Criteria:

• A history of septic arthritis in the joint to operate
• Amputations
• Neurological deficits
• Inability to complete the questionnaires because of cognitive or language difficulties
• Prior knee arthroplasty in the joint to operate
• Prior arthroplasty in another weight-bearing joint within the last 6 months