ANKLE Human ankle cartilage deformation after different in vivo impact conditions Ans Van Ginckel • Fredrik Almqvist • Koenraad Verstraete • Philip Roosen • Erik Witvrouw Received: 18 December 2009 / Accepted: 19 April 2010 Ó Springer-Verlag 2010 Abstract Recently, the general finding of increased ankle cartilage stiffness to loading has been challenged, suggesting the need for the investigation of different in vivo loading conditions. Therefore, the objectives of the present study were to determine ankle (talar) cartilage deformation after in vivo loading using 3D volume change calculation and to establish any difference in volume change between four weight-bearing exercises. The four exercises represented increasing impact (bilateral knee bends \ unilateral knee bends\ drop jumps) as well as two types of loading: dynamic and static loading (i.e. unilateral knee bends and unilateral static stance). Based on MRI, 3D reconstructions of talar cartilage were generated to determine 3D volumes before and after four exercises in 13 healthy subjects (bilateral and unilateral knee bends, static unilateral stance, drop jumps). Mean talar deformation (volume decrease) was 8.3% after bilateral knee bends (P = 0.001), 7.7% after unilateral knee bends (P = 0.020), 14.6% after unilateral static stance (P \ 0.001), 12.5% after drop jumps (P = 0.001). Statisti- cal analysis also revealed deformation to be significantly higher after unilateral static stance than after unilateral knee bends (P = 0.017). These results suggest that talar cartilage endures substantial deformation during in vivo loading characterized by more deformation (i.e. higher volume change) after static than after dynamic loading. Keywords In vivo Á Exercise Á Ankle Á Cartilage Introduction The primary function of articular cartilage consists of stress dissipation, providing a frictionless surface during joint motion and improving joint surface congruence [7]. To fulfil these tasks, articular cartilage presents as a highly organized and complex tissue. The interplay between biochemical composition, ultrastructural organization and interaction between matrix constituents is generally known to charac- terize the tissue’s biomechanical characteristics such as deformational behaviour. Being an avascular, aneural and alymfatic tissue, it is the cartilage matrix and its compounds that are of utmost importance for load transmission. This interstitial matrix consists for 70% of fluid and for 30% of A. Van Ginckel PhD fellow Research Foundation-Flanders, Brussels, Belgium A. Van Ginckel (&) Á E. Witvrouw Department of Rehabilitation Sciences and Physiotherapy, Ghent University, UZ Campus, 3B3, De Pintelaan 185, 9000 Ghent, Belgium e-mail: Ans.VanGinckel@UGent.be E. Witvrouw e-mail: Erik.Witvrouw@UGent.be F. Almqvist Department of Physical Medicine and Orthopaedic Surgery, Ghent University, UZ Campus, De Pintelaan 185, Ghent, Belgium e-mail: Fredrik.Almqvist@UGent.be K. Verstraete Department of Radiology, Ghent University, UZ Campus, De Pintelaan 185, Ghent, Belgium e-mail: Koenraad.Verstraete@UGent.be P. Roosen Department of Rehabilitation Sciences and Physiotherapy, Artevelde University College, UZ Campus (3B3), De Pintelaan 185, Ghent, Belgium e-mail: Philip.Roosen@UGent.be 123 Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-010-1159-4