CORR Insights®: Are TKA Kinematics During Closed Kinetic Chain Exercises Associated with Patient-reported Outcomes? A Preliminary Analysis.

Despite the extensive analysis of knee kinematics before and after TKA, the links to postoperative patient-reported outcomes have been less-than compelling. Some reasons for this include the differences in the biomechanics of the post-TKA knee relative to normal knees, the high patient-to-patient variation in kinematics, patient selection bias, and the activities studied being limited by the fluoroscopic field of view. Previous studies have shown that certain kinematic features, such as paradoxical or reverse roll-back and condylar lift-off, have negative biomechanical consequences but they have yet to be conclusively linked to clinical patientreported outcomes [3, 6, 7]. The kinematics of open-kinetic-chain knee extension are driven largely by the extensormechanism and by tibiofemoral articular geometry. Closed-kinetic-chain knee extension, with the foot planted on the ground, generates higher knee forces, is subject to greater anteroposterior motion, condylar lift-off, and axial rotation, and therefore has potential for unmasking instability [3, 6, 7]. The prospective study by Van Onsem and colleagues [14] comes closest of all the studies I have read thus far to linking specific patterns of post-operative kinematics to patient-reported outcomes. The authors found differences in closed-chain kinematics between clusters of patients with disparate patient-reported outcome measures (PROMs), but theywere careful not to speculate on the biomechanical reasons for the differences in knee kinematics. They appropriately qualified the title of their study as “A Preliminary Analysis” because their study raises more questions than it answers.