A blinded, three-arm randomised trial assessing joint function and measuring three-dimensional knee joint kinematics in individuals six months after a total knee joint replacement; comparing a medially stabilised design, to standard fixed bearing conventional designs – posterior stabilising and cruciate retaining

Background: No randomised trial exists to assess the relative prosthetic performance of three fixed bearing total knee joint replacement construct designs through clinical functional outcomes and biomechanical gait analysis at six months after the index procedure. Methods: The design of a double blinded, prospective, randomised trial with three parallel patient groups is presented.   Patients reviewed in consultant clinic with radiographic and clinical diagnosis of osteoarthritis of the knee, with the condition deemed severe enough to require a total knee joint replacement (TKJR) are eligible.  Subjects enrolled in the trial are randomised to one of the three TKJR construct designs approximately ten days prior to scheduled date of surgery.  Each subject is then followed up for at least twelve months.  Repeated measure of Analysis of Variance (ANOVA), and Analysis of Covariance (ANCOVA) will be utilised to uncover any clinical functional differences in each trial group in each time interval. Results: Differences in clinical functional scores at each time interval compared to pre-intervention, as well as between group differences in clinical functional scores at each time interval will be examined.  At six months after the operation, biomechanical measurements of joint motion, ground reaction forces, and muscle electromyographic (EMG) activity will be recorded simultaneously from each subject for four test conditions: level walking, stair ascent, stair descent, and chair rise. Conclusions: This randomised trial is designed to better understand the relationships between the clinical functional outcomes and replaced knee kinematics in three fixed bearing total knee replacement construct designs at six months postoperatively.