impact of orthotics on the knee

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

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ComponentsExample:

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

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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 = 10.8⁰cos 10.8⁰ = (vc / 150)

vc = 147.34 lbSin 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

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