Abstract
<title>Abstract</title> <p>Introdution: The ankle joint comprises the tibiotalar joint and the distal tibiofibular joint. Although the distal tibiofibular joint has limited motion, its dysfunction significantly affects lower extremity biomechanics. However, the three-dimensional kinematic relationship between these two joints during gait remains unclear. Methods The three-dimensional motions of 32 distal tibiofibular joints and tibiotalar joints from 16 healthy adults (8 males, 8 females) were analyzed during normal gait. CT scans were used to create 3D bone models of the tibia, fibula, and talus. X-ray images from seven gait phases were selected for 2D-3D and 3D-3D registration to quantify the six-degree-of-freedom kinematics. Results During gait, distinct kinematic patterns were observed in both joints. In the distal tibiofibular joint, the fibula exhibited rotational ranges of motion (ROM) of 0.67 ± 0.27° (plantarflexion/dorsiflexion), 0.18 ± 0.1° (inversion/eversion), and 1.18 ± 0.62° (internal/external rotation). Translational ROMs were 1.95 ± 0.79 mm (medial/lateral), 2.65 ± 1.13 mm (anterior/posterior), and 1.91 ± 1.12 mm (superior/inferior). In the tibiotalar joint, internal–external rotation (ROM: 15.53° ± 6.08°) and plantarflexion–dorsiflexion (ROM: 14.92° ± 5.71°) were the predominant motions. Talar motion exhibited strong coupling: plantarflexion was highly correlated with anterior and inferior translation (r = 0.85), whereas dorsiflexion was highly correlated with posterior and superior translation. Conclusion The distal tibiofibular joint exhibits coupled motion with the tibiotalar joint during normal gait, though independent movement patterns persist. These six-DOF kinematic data provide an in vivo reference for understanding ankle joint biomechanics.</p>