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TRANSCRIPT
Impact of Orthotics on the Knee
Sara Mrowzinski
http://www.wmgh.net/article/foot-orthotics-72.asp
Introduction Many people think of orthotics based
on the off-the-shelf brands and do not realize how the orthotic works
What is an Orthotic?
Prevents abnormal movement
Various conditions can be relieved› Back, hip, knee,
and ankle pain Increase stability in
joints Increase
biomechanical efficiency
Right leg posterior view
http://www.wellfeet.com/orthoticswork.htm
The Knee
Anatomically designed to flex and extend in the sagital plane (hinge joint)
Abnormal alignment at the foot can alter the forces when standing, walking, running, etc. to a transverse component
Pronation
70% have over-pronation
Low arches
Effects travel up
http://healthyfeetforlife.com/
Components
Example: 150 lb person standing with the foot 20⁰ over-pronated
Vertical Component:cos 20⁰ = (v / 150)
v = 140.95 lb
Transverse Component: sin 20⁰ = (t / 150)
t = 51.3 lb
Correction Force directed at the ankle into the
posted orthotic
http://www.orthoticsandal.com/AboutOS_Technology.html
Correction
http://www.trcc.com/au/solution/orthotics.html
http://www.wellfeet.com/orthoticswork.htm
“Effect of Inverted Orthoses on Lower-Extremity Mechanics in Runners”
Authors: › Dorsey S. Williams III› Irene McClay Davis› Stephen P. Baitch
Journal: › Medicine & Science in Sports & Exercise
Methods
11 runners participated All previously wore standard orthotics Inversion orthotics posted at 15⁰ or 25⁰ 3-D gait analysis
› Joint motion› Joint kinetics
Ran at 3.35 m/s
Results
Results› Eversion moment not present before› Peak inversion moment significantly
decreased› Increase in peak knee adduction
Other factors› Takes 5⁰ of change in post in order to have
1⁰ change effect
Results Continued
Example Corrected with 54%
improvement
20⁰ x .54 = 10.8⁰
cos 10.8⁰ = (vc / 150)vc = 147.34 lb
Sin 10.8⁰ = (tc / 150)tc = 28.11 lb
(28.11-51.3) x 100% = 45% decrease
51.3
Discussion Impact of Padding
› Decreases the force due to the compression of the padding
› Orthotics have various amounts of padding depending on the person’s needs
At the ankle› Muscles affect stability
Rear foot movement and stress on the lateral knee needs to be studied more
Conclusions
These results suggest that an inversion orthotic may be more suitable than a standard orthotic for those with excess pronation
http://www.syracuseorthotics.com/