title: How crouch gait can dynamically induce stiff-knee gait.
abstract: Children with cerebral palsy frequently experience foot dragging and tripping during walking due to a lack of adequate knee flexion in swing (stiff-knee gait). Stiff-knee gait is often accompanied by an overly flexed knee during stance (crouch gait). Studies on stiff-knee gait have mostly focused on excessive knee muscle activity during (pre)swing, but the passive dynamics of the limbs may also have an important effect. To examine the effects of a crouched posture on swing knee flexion, we developed a forward-dynamic model of human walking with a passive swing knee, capable of stable cyclic walking for a range of stance knee crouch angles. As crouch angle during stance was increased, the knee naturally flexed much less during swing, resulting in a 'stiff-knee' gait pattern and reduced foot clearance. Reduced swing knee flexion was primarily due to altered gravitational moments around the joints during initial swing. We also considered the effects of increased push-off strength and swing hip flexion torque, which both increased swing knee flexion, but the effect of crouch angle was dominant. These findings demonstrate that decreased knee flexion during swing can occur purely as the dynamical result of crouch, rather than from altered muscle function or pathoneurological control alone.
authors.affiliation: Department of Rehabilitation Medicine, Research Institute MOVE, VU University Medical Center, PO Box 7057, 1007 MB Amsterdam, The Netherlands. mmvanderkrogt@gmail.com
authors.forename: Marjolein M
authors.initials: MM
authors.lastname: van der Krogt
authors.forename: Daan J J
authors.initials: DJ
authors.lastname: Bregman
authors.forename: Martijn
authors.initials: M
authors.lastname: Wisse
authors.forename: Caroline A M
authors.initials: CA
authors.lastname: Doorenbosch
authors.forename: Jaap
authors.initials: J
authors.lastname: Harlaar
authors.forename: Steven H
authors.initials: SH
authors.lastname: Collins
mesh_terms: D002547:Cerebral Palsy / Q000150:complications / Q000503:physiopathology*; D003198:Computer Simulation; D055119:Elastic Modulus; D005684:Gait; D020233:Gait Disorders, Neurologic / Q000209:etiology / Q000503:physiopathology*; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008954:Models, Biological; D011187:Posture