Medial Unicompartmental Knee Arthroplasty Restores Native Knee Kinematics During Activities of Daily Living: A Pilot Study

The ability of unicompartmental knee arthroplasty (UKA) to restore native knee kinematics during activities of daily living remains unclear. The objectives of this prospective study were to identify changes in knee kinematics after medial UKA (mUKA) and to determine if mUKA restores native knee kinematics during activities of daily living. We hypothesized that kinematics are different between the mUKA knee and contralateral knee before surgery, that mUKA restores native knee kinematics, and that mUKA does not affect lateral compartment dynamic joint space. Nine participants performed walking, chair rise, stair ascent and stair descent within a biplane radiography system before and after mUKA. Bilateral knee kinematics were determined for each activity using a validated tracking process that matched subject-specific bones and implants to the biplane radiographs. Compared to contralateral knee, the pre-UKA knee was more adducted (p <= 0.019), and more laterally translated (p <= 0.008) during all four activities. Additionally, compared to contralateral knee, pre-UKA knee was less internally rotated (p <= 0.044) during chair rise and stair ascent. Lateral compartment dynamic joint space did not change during any activity from pre to post mUKA. Our results indicate that mUKA generally restores native kinematics during activities of daily living without altering lateral compartment dynamic joint space.