The proposed study is a retrospective, observational study. A group of 5 subjects with the AttuneTM cruciate retaining (CR) fixed bearing total knee arthroplasty (TKA) are analysed during level walking, a deep knee bend, sitting down onto a chair, standing up from a chair and stair descent at least 12 months post-operatively, in terms of 3D fluoroscopic assessed tibio-femoral TKA motion as well as simultaneous skin marker assessed whole leg motion and ground reaction forces. The obtained information helps the manufacturer (DePuy) to evaluate, bring to market and advance the implant. Furthermore the information will be integrated in a model, which will be developed at the Center for Orthopaedic Engineering, University of Denver. By means of this model, different conditions such as the use of an advanced prosthesis design can be simulated and tested.

The objective of this study is in a first step to demonstrate the capability of data collection and analysis of level gait, deep knee bend, sitting down onto a chair, standing up from a chair and stair descent on a limited sample size of five subjects. Secondly to quantify and describe the three-dimensional kinematics for the cruciate retaining (CR), fixed bearing AttuneTM TKA during daily activities such as those mentioned.

Inclusion Criteria:

• Unilateral TKA (ATTUNETM) due to osteoarthrosis (OA)
• Body mass index (BMI) ≤ 33
• Good clinical outcome, Knee injury and Osteoarthritis Outcome Score (KOOS) > 70
• No or very low Visual Analog Scale for Pain (VAS) < 2
• At least one year post-op
• Standardized general health survey score (SF-12) within the normal range for people in their age group

Exclusion Criteria:

• Actual significant problem on lower extremities
• Misaligned TKA
• Any other arthroplasty at the lower extremities
• Patient incapable to understand and sign informed consent
• Incapable of performing the motion tasks
• Pregnancy

Prof. Dr. med. Carsten Perka will do the recruitment, since he is the surgeon that worked the most with this implant and therefore also has the biggest population of possibly eligible patients. Furthermore the patients already know and trust him, which could lead to a greater success in the recruitment as well. For these reasons the financial source DePuy Synthes, Johnson and Johnson, requires that the clinical collaborator Prof. Dr. med. Carsten Perka will do the recruitment. He works in the Charité in Berlin, Germany, where he does the recruitment.