Purpose: The purpose of this pilot study was to determine the radius of curvature of the tibia and talus, and to deduce ankle joint kinematics in the sagittal plane using passive imaging data. Methods: Imaging data of four subjects under passive conditions was used. Ligament positions were marked using MRI data to subscribe the four-bar linkage (FBL) mechanism at the ankle joint. Flexion motion of the assembly construct was simulated in the sagittal plane to determine the contact points on the tibial and talar dome surfaces. The radius of curvature was determined by fitting the contact points with a circle fit. Results: In addition to articular surfaces, calcaneofibular and tibiocalcaneal ligaments in the FBL play an important role in affecting the path of ankle joint motion. Two different linkage arrangements between the ligaments were observed in this study. The double-crank type arrangement by these ligaments generated the same contact path on the articular surface during dorsi- and plantarflexion, whereas the triple-rocker arrangement resulted in different paths. Conclusion: A higher order compliant mechanism, which includes additional ankle ligaments, needs to be developed and studied under load bearing conditions to achieve more accurate results. [ABSTRACT FROM AUTHOR] Copyright of Computer Methods in Biomechanics & Biomedical Engineering: Imaging & Visualisation is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)