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Anatomical Knee Joint

IP.com Disclosure Number: IPCOM000091868D
Original Publication Date: 1968-Jun-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Freudenstein, F: AUTHOR [+2]

Abstract

Simulation of a true knee action is provided by fitting the upper-leg and lower-leg centrodes of a knee joint with gear members. These are respectively shaped and interrelated to produce a constrained rolling motion of the centrodes relative to each other. Upper-leg member 1 and lower-leg member 2 are shown in sitting position. Attached to member 1 is upper-leg plate 3 carrying the upper-leg centrode gear 4. Attached to member 2 is lower-leg plate 5 carrying the lower-leg centrode gear 6, upon which gear 4 rolls during the bending movements of the joint. Gears 4 and 6 have noncircular pitch configurations, e.g., log spiral. Other combinations of shapes can be utilized as explained. Circular pin 7 on plate 3 rides in curved slot 8 in plate 5.

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Anatomical Knee Joint

Simulation of a true knee action is provided by fitting the upper-leg and lower-leg centrodes of a knee joint with gear members. These are respectively shaped and interrelated to produce a constrained rolling motion of the centrodes relative to each other. Upper-leg member 1 and lower-leg member 2 are shown in sitting position. Attached to member 1 is upper-leg plate 3 carrying the upper- leg centrode gear 4. Attached to member 2 is lower-leg plate 5 carrying the lower-leg centrode gear 6, upon which gear 4 rolls during the bending movements of the joint. Gears 4 and 6 have noncircular pitch configurations, e.g., log spiral. Other combinations of shapes can be utilized as explained. Circular pin 7 on plate 3 rides in curved slot 8 in plate 5.

The relative motion between members 1 and 2 in the plane of the drawing is determined by the shapes of the pitch profiles of gears 4 and 6. The positiveness of this motion is ensured by the constraint of pin 7 moving in slot 8. The shape of slot 8 is a function of the shapes of gears 4 and 6 and can be determined by well-known methods. Constraints against motion transverse to the plane of the drawing can be standard in arrangement.

With two log spiral gears working together as shown, possible centrode shapes are as follows. The upper-leg centrode radius of curvature equals 0.3 (1 + 2s) and the lower-leg centrode radius of curvature equals 0.75 (1 - 2s) where s is the arc length, maximum inches. If the u...