Impact of Alignment Strategies on Knee Biomechanics and Muscle Activation During Squatting After Total Knee Arthroplasty

Inverse kinematic alignment (iKA), which preserves the natural knee oblique joint line in total knee arthroplasty, has been shown to produce lower-limb kinematics similar to healthy controls during gait. However, its ability to maintain this advantage during more demanding activities remains unclear. This study evaluated lower-limb kinematics and muscle activation patterns during squatting in individuals who underwent iKA, adjusted mechanical alignment (aMA), and healthy controls. Kinematics were analyzed using a 3D Vicon system, while muscle activation patterns were recorded using electromyography. The iKA group (80.36° [27.43°]) exhibited knee range of motion comparable to healthy controls (95.25° [23.33°]), while the aMA group (67.39° [28.52°]) showed a significant difference (P = .004). Additionally, the aMA group showed reduced hip flexion compared with controls during squatting (P < .001). Although both iKA and aMA groups displayed differences in hip extension and ankle dorsiflexion compared with controls, no differences in muscle activation patterns were observed. These findings suggest that the iKA and aMA groups can squat without altering muscle activity patterns. However, iKA demonstrates biomechanical outcomes that resemble those of healthy controls in certain aspects. Persistent strength deficits in both surgical groups highlight the need for targeted rehabilitation to restore strength.