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First published online June 29, 2007
Journal of Experimental Biology 210, 2548-2562 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02792

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Running in ostriches (Struthio camelus): three-dimensional joint axes alignment and joint kinematics

Jonas Rubenson^1,*, David G. Lloyd¹, Thor F. Besier², Denham B. Heliams³ and Paul A. Fournier¹

¹ School of Human Movement and Exercise Science, The University of Western Australia, Crawley, WA, 6009, Australia,
² Department of Orthopaedics, Stanford University, 341 Galvez St, Stanford, CA 94305, USA
³ Fauna Technology, PO Box 558, Gosnells, WA, 6990, Australia

^* Author for correspondence (e-mail: jrubenson{at}csupomona.edu)

Accepted 16 May 2007

Although locomotor kinematics in walking and running birds have been examined in studies exploring many biological aspects of bipedalism, these studies have been largely limited to two-dimensional analyses. Incorporating a five-segment, 17 degree-of-freedom (d.f.) kinematic model of the ostrich hind limb developed from anatomical specimens, we quantified the three-dimensional (3-D) joint axis alignment and joint kinematics during running (at 3.3 m s^–1) in the largest avian biped, the ostrich. Our analysis revealed that the majority of the segment motion during running in the ostrich occurs in flexion/extension. Importantly, however, the alignment of the average flexion/extension helical axes of the knee and ankle are rotated externally to the direction of travel (37° and 21°, respectively) so that pure flexion and extension at the knee will act to adduct and adbuct the tibiotarsus relative to the plane of movement, and pure flexion and extension at the ankle will act to abduct and adduct the tarsometatarsus relative to the plane of movement. This feature of the limb anatomy appears to provide the major lateral (non-sagittal) displacement of the lower limb necessary for steering the swinging limb clear of the stance limb and replaces what would otherwise require greater adduction/abduction and/or internal/external rotation, allowing for less complex joints, musculoskeletal geometry and neuromuscular control. Significant rotation about the joints' non-flexion/extension axes nevertheless occurs over the running stride. In particular, hip abduction and knee internal/external and varus/valgus motion may further facilitate limb clearance during the swing phase, and substantial non-flexion/extension movement at the knee is also observed during stance. Measurement of 3-D segment and joint motion in birds will be aided by the use of functionally determined axes of rotation rather than assumed axes, proving important when interpreting the biomechanics and motor control of avian bipedalism.

Key words: kinematics, ostrich, bird, three-dimensional, locomotion, joint

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