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BACKGROUND: There is a greater risk of tibial component loosening when mobile unicompartmental knee replacement is performed in anterior cruciate ligament deficient knees. We previously reported on a cohort of anterior cruciate ligament deficient patients (n=46) who had undergone surgery, but no difference was found in implant survivorship at a mean 5-year follow-up. The purpose of this study was to examine the kinematic behaviour of a subcohort of these patients. METHODS: The kinematic behaviour of anterior cruciate deficient knees (n=16) after mobile unicompartmental knee replacement was compared to matched intact knees (n=16). Sagittal plane knee fluoroscopy was taken while patients performed step-up and forward lunge exercises. The patellar tendon angle, knee flexion angle and implant position was calculated for each video frame. FINDINGS: The patellar tendon angle was 5° lower in the deficient group, indicating greater anterior tibial translation compared to the intact group between 30 and 40° of flexion. Large variability, particularly from 40-60° of flexion, was observed in the bearing position of the deficient group, which may represent different coping mechanisms. The deficient group took 38% longer to perform the exercises. INTERPRETATION: Kinematic differences were found between the deficient and intact knees after mobile unicompartmental knee replacement; but these kinematic changes do not seem to affect the medium-term clinical outcome. Whether these altered knee kinematics will have a clinical impact is as yet undetermined, but more long-term outcome data is required before mobile unicompartmental knee replacement can be recommended for an anterior cruciate ligament deficient patient.

Original publication




Journal article


Clin biomech (bristol, avon)

Publication Date





33 - 39


Anterior cruciate ligament, Function, Knee kinematics, Patellar Tendon Angle, Unicompartmental knee replacement, Aged, Aged, 80 and over, Anterior Cruciate Ligament, Arthroplasty, Replacement, Knee, Biomechanical Phenomena, Case-Control Studies, Female, Fluoroscopy, Humans, Joint Instability, Knee Joint, Male, Middle Aged, Patellar Ligament, Range of Motion, Articular, Tibia