Objective To assess the biomechanical differences between the artificial ankle joints INBONE II and INFINITY after total ankle arthroplasty (TAA) to provide more scientific and individualized treatment options for patients. Methods A patient-individualized TAA lower extremity MSK MBD model was established using the musculoskeletal (MSK) multibody dynamics (MBD) software AnyBody. The ankle joint contact force, motion, and contact characteristics of artificial ankle joint surfaces were predicted. Results The geometric shape of the articular surface of the artificial ankle had no significant effect on the ankle contact force, but it affected the range of motion and contact characteristics of the articular surface. Compared with INBONE II, the coronal plane articular surface arc height of INFINITY was lower, and increased the inversion-eversion and external rotation-internal rotation movements by 7.91% and 2.61%, respectively. Sagittal plane matching was lower, and reduced posterior-anterior and inferior-superior movements by 21.75% and 21.23%, respectively, and medial-lateral movement increased by 49.26%. INFINITY exhibited lower matching with decreases of 18.48%, 30.42%, and 26.36% in the medial, lateral, and total joint surface contact areas, respectively. However, the center of the pressure motion trajectory was concentrated on the medial side, while avoiding edge contact stress concentration and reducing the risk of joint dislocation and premature wear of the tibial component. Conclusions The smaller geometric constraints of the INFINITY artificial ankle joint demonstrated better biomechanical performance, thereby promoting improved postoperative ankle joint functional recovery.