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Dear Netters:
I just thought I would add something to Peter Hamer's response
concerning ACL mechanism of injury. Although the primary responsibility of the
ACL is to prevent anterior translation of the tibia on the femur, it also acts
to check external rotation of the tibia during knee flexion and also check
extension and hyperextension of the knee. While I agree with Peter that the
Lachman's and anterior drawer tests may only determine uni-planar anterior
stability, we must consider that anteromedial or anterolateral rotary
instabilities often accompany an ACL tear. Tests such as the Slocum and
Lateral Pivot Shift are used to determine these respective instabilities. The
common mechanism of injury of the ACL occurs when the foot is fixed to the
ground while the femur rotates on the tibia. However, in sports such as hockey
and skiing ACL tears can occur while the lower leg is positioned in an "open
kinetic chain". While the lower extremity is positioned in this open kinetic
chain, the tibia rotates on the femur causing the ACL sprain. I hope this
helps...
Mitch
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* Mitchell L. Cordova MA, ATC * e-mail mcordov@uoft02.utoledo.edu *
* Ph.D Candidate - Biomechanics * phone (419) 537-2753 *
* Dept. of HPHP * fax (419) 537-7719 *
* The University of Toledo * *
* Toledo, OH 43606-3390 USA * *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
I just thought I would add something to Peter Hamer's response
concerning ACL mechanism of injury. Although the primary responsibility of the
ACL is to prevent anterior translation of the tibia on the femur, it also acts
to check external rotation of the tibia during knee flexion and also check
extension and hyperextension of the knee. While I agree with Peter that the
Lachman's and anterior drawer tests may only determine uni-planar anterior
stability, we must consider that anteromedial or anterolateral rotary
instabilities often accompany an ACL tear. Tests such as the Slocum and
Lateral Pivot Shift are used to determine these respective instabilities. The
common mechanism of injury of the ACL occurs when the foot is fixed to the
ground while the femur rotates on the tibia. However, in sports such as hockey
and skiing ACL tears can occur while the lower leg is positioned in an "open
kinetic chain". While the lower extremity is positioned in this open kinetic
chain, the tibia rotates on the femur causing the ACL sprain. I hope this
helps...
Mitch
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* Mitchell L. Cordova MA, ATC * e-mail mcordov@uoft02.utoledo.edu *
* Ph.D Candidate - Biomechanics * phone (419) 537-2753 *
* Dept. of HPHP * fax (419) 537-7719 *
* The University of Toledo * *
* Toledo, OH 43606-3390 USA * *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *