Introduction

Recent studies show that Model-based Roentgen Stereophotogrammetric Analysis is superior to the conventional in vivo measurements of polyethylene liner wear in total knee prostheses. Although it is generally postulated that weight-bearing (standing) views are required to detect liner wear, most RSA images are acquired in non-weight-bearing (supine) view for practical reasons. Therefore, it would be of interest to know if supine views would be sufficient for measuring TKA liner wear, defined as a change in minimum joint space width (mJSW). As a difference in mJSW between weight-bearing and non-weight-bearing RSA images has never been validated, the aim of this study is to compare the outcome of in vivo measurements of mJSW in total knee prosthesis when conducted with weight-bearing and non-weight-bearing RSA views.