Human KneeJoint Mechanics Module Development

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Human Knee-Joint Mechanics Module Development

• Dr. Robert Freeman
• Ms. Julie L. Fife
• University of Texas - Pan American
• July 30, 2004

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Project Goals

• To investigate the functional anatomy of the
• human knee using a number of distinct sagittal
• plane models
• Tibiofemoral Joint Variants
• Simple hinge joint model
• Cruciate linkage model
• Single-point surface contact model
• Patellofemoral Joint Variants
• Single-point patella model
• Rigid-body patella model

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Challenge 1
Can voluntary contraction of the quadriceps
muscle group tear the ACL during an isometric
knee extension exercise?
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Cruciate Linkage Model with Single-Point Patella
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Working Model 2D Version of Cruciate Linkage Model

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Exercises leading to Challenge 1

• Exercise 1 What "knee" muscles and ligaments are
  active during Knee extension?
• Consider only sagittal plane motion.
• Exercise 2 Draw a FBD of the Tibia for an
  isometric knee-extension exercise.
• Assume the ankle/foot is rigidly attached to the
  tibia and that there is no friction between the
  femoral condyles and the (flat) tibial plateau.
• Exercise 3 Given the patellar-tendon force as a
  function of the flexion angle FPT(q), compute the
  force in the ACL as a function of flexion angle.
• Given that the maximum force that the ACL can
  withstand is 2000N, answer the challenge.

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Challenge 2

• What constraint forces and moment are required to
  keep the femur fixed during the isometric knee
  extension exercise of challenge 1?

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Challenge 3a

• Consider knee flexion during an isometric leg
  curl exercise.
• Develop an appropriate FBD and solution procedure
  required to determine if you can voluntarily tear
  either your ACL or PCL.

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Challenge 3b

• Consider knee extension during an isometric
  squat-to-stand exercise.
• Develop an appropriate FBD and solution procedure
  required to determine the maximum weight you can
  squat.

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Challenge 4

• Create your own WM2D Cruciate Linkage model of
  the knee.
• Follow the steps detailed in
• CruciateLinkDev.doc
• And the associated tutorial videos

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Patellar Tendon Force

• The patellar tendon force (in Newtons) is given
  below as the fifth order polynomial in the
  flexion angle ? (in degrees).
• This polynomial was obtained as an approximation
  of the results given in Figure 6 of Serpas, et.al.

Fpt(?) 439.106 (305.71?1) (-18.185?2)
(0.554?3) (-6.674 x 10-3?4) (2.5x10-5?5)
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