Related Experiment Video
Updated: Aug 14, 2026
Sit-to-stand-and-walk from 120% Knee Height: A Novel Approach to Assess Dynamic Postural Control Independent of Lead-limb
Published on: August 30, 2016
Directly segmented versus rigid-transformation-based contact-area measurement in weight-bearing knee cartilage:
Hyo-Bin Lee1, Sung-Eun Hong2, Jang-Hwan Choi3
1Department of Computational Medicine, Graduate Program in System Health Science and Engineering, Ewha Womans University, South Korea.
Abstract:
Conventional "rigid-transformation-based contact area" methods calculate tibiofemoral contact area by rigidly transforming supine-segmented cartilage using bone registration matrices, thereby preserving unloaded cartilage geometry without explicitly representing load-induced changes in cartilage thickness, surface shape, or lateral expansion. This pilot study compared the biomechanical validity of directly segmented contact-area measurement (direct cartilage segmentation at each time point) with that of rigid-transformation-based methods under sustained weight-bearing. Seven healthy subjects underwent cone-beam computed tomography at a non-weight-bearing supine baseline and six standing time points (5 s to 15 min). The directly segmented contact area demonstrated a consistent monotonic increase across all available time points in every subject, a pattern consistent with time-dependent cartilage compression. Conversely, the rigid-transformation-based contact area showed irregular fluctuations without consistent temporal trends, indicating that the method did not reproduce time-dependent creep behavior. Among the five subjects with paired measurements, the directly segmented measurements significantly exceeded rigid-transformation-based values from 15 s onward (p < 0.05), with the divergence widening progressively over time. Phase-specific area-based compression-rate analysis revealed 31-fold higher rates during the early phase (0-5 s) compared with the sustained phase (5 s to 5 min), reflecting the transition from elastic deformation to fluid exudation-dominated biphasic behavior. Regional analysis demonstrated mean contact-area increases across all 18 tibial plateau regions with minimal centroid displacement (∼1 mm), indicating symmetric, concentric expansion rather than directional shift. These findings support directly segmented contact-area measurement as a biomechanically consistent approach for weight-bearing studies, whereas rigid-transformation-based methods do not reproduce time-dependent contact-area expansion because loaded cartilage deformation is not represented.
