Kinematic analyses of gait
* denotes sections that contain background material that is not included in course objectives.
Kinematic measures of gait
kinematic variables describe the extent, speed, and direction of movement of joints or body segments
· step length
· stride length
· velocity
· cadence
Summary of gait kinematics
The chart (adapted from Mann, 1975, Fig. 13-18, p. 266; Rodgers, 1988, Fig. 1, p. 1823; Chan & Rogers, 1994; Mann & Mann, 1997, Fig. 7.24, p. 149) summarizes the kinematic interactions that occur during the gait cycle. The chart's rows distinguish between stance and swing phases.
Summary of
References
Chan, C.W., & Rudins, A. (1994). Foot biomechanics during walking and running. Mayo Clinic Proceedings, 69, 448-61.
Mann, R.A. (1975). Biomechanics of the foot. In American Academy of Orthopaedic Surgeons (Ed.), Atlas of orthotics: Biomechanical principles and application (pp. 257-266). St. Louis: C.V. Mosby.
Mann, R.A., & Mann, J.A. (1997). Biomechanics of the foot. In B. Goldberg & J.D. Hsu (Eds.), Atlas of orthoses and assistive devices (pp. 135-152). St. Louis: C.V. Mosby.
Rodgers, M.M. (1988). Dynamic biomechanics of the normal foot and ankle during walking and running. Physical Therapy, 68, 1822-1830.
*The determinants of normal and pathological gait
Features of the movement pattern that minimize displacement in the body's center of gravity during gait:
5. Knee Ankle Foot Interactions
Examples of how these kinematic features produce an efficient walking pattern:
· During double limb support, that time when the center of gravity is at its lowest point, joint angles in both lower extremities are such that their effective lengths are maximized. Additionally, the pelvis is rotated forward on the side where the limb is in loading response, and backward on the limb which is in preswing. This functional lengthening of the limbs minimizes the vertical drop in the center of gravity.
· During midstance and midswing, when the center of gravity is highest, the stance limb's hip, knee, and ankle are all flexed 5 degrees. In addition, the pelvis is tilted downward laterally toward the swing limb. This minimizes the center of gravity's upward excursion, keeping it lower than if the individual were standing erect.
· The six "determinants" are logically appealing, because they help us focus on a relatively small number of critical factors from among the many degrees of mechanical freedom that are possible during walking. However, very recent research questions whether the determinants are important, at least for the reasons that Inman and Saunders proposed:
· Kirtley, C. (Oct. 20, 1999). Frequently asked questions about clinical gait analysis: Determinants of Gait. Retrieved March 27, 2001 from August 24, 2000, from Clinical Gait Analysis web site: http://guardian.curtin.edu.au/cga/faq/determinants.html
· Kerrigan, D.C. (2001). Aesthetics of walking [Electronic version]. Journal of Rehabilitation Research and Development, 38 (5), ix-x.
CENTER OF GRAVITY DISPLACEMENTS
During ambulation, the body's center of gravity is propelled forward. However it also moves vertically and laterally; we presume a gait pattern to be energy efficient to the extent that it minimizes vertical and lateral displacements.
I. Vertical displacement of COG
Viewed in the sagittal plane, the vertical displacement of the center of gravity traces a smooth sinusoidal curve. This curve's amplitude in the normal adult male is approximately 5 cm or 2 inches. The center of gravity moves vertically through two full oscillations during each gait cycle, so that the curve has two peaks and two troughs.
· The low points or troughs in the sinusoidal pathway occur during the gait cycle's two periods of double limb support (loading response and preswing). The depth of the troughs is limited by:
· Knee-ankle-foot interactions
· The high points or peaks occur at midstance and again at midswing. The height of these peaks is limited by:
II. Lateral displacement of COG
The center of gravity also oscillates laterally during ambulation. The total lateral displacement traces a sinusoidal curve with an amplitude of approximately 6 centimeters or 2.5 inches. The greatest lateral excursion of the center of gravity occurs at the end of midstance. Thus, only one full lateral oscillation of the center of gravity (to the right and left) occurs during a gait cycle. The amplitude of this lateral excursion is limited by a structural feature in the lower extremities, namely genu valgus.
To obtain a complementary perspective, view Chris Kirtley's kinematics web page, which covers some of the same material as this page.
Last updated 3-27-02 Dave Thompson PT
Introduction to the study of walking
This is one of the first pages developed during this web education project, which began February 20, 1996.
