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Author Topic: What's shearing? How to avoid shearing in the knee?  (Read 4465 times)

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Offline margret

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What's shearing? How to avoid shearing in the knee?
« on: March 13, 2013, 09:47:59 PM »
I had cartilage repair on the back of my kneecap, and I'm trying to understand the knee as best I can to give the cartilage a chance to grow. I've read that shearing forces are damaging to cartilage, while compressive forces are beneficial. Does anyone know how to minimize shearing forces in ordinary daily life?

I know that sudden, dramatic twists of the knee over a planted foot are a problem, and I'm not pushing past my doctor's instructions in any way. But I don't know whether shearing forces are also a problem when you're just ambling around the house on crutches, occasionally twisting to reach for a towel on a rack, or turning a corner... Am I being paranoid, or are damaging shearing forces still possible in the daily life of a VERY cautious person?

Offline kimb

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Re: What's shearing? How to avoid shearing in the knee?
« Reply #1 on: March 13, 2013, 09:59:41 PM »
It is kind of hard to explain, but it mostly applies to things that put excess forces on the kneecap as it slides along the femoral groove. Moving around normally should not cause you any problems. Things that could cause problems include leg extensions (ones done on leg ext. machines at the gym) deep squats and lunges. Especially when people do them with poor form, or don't have the flexibility to do them correctly. Any time you bend and allow your knee to come forward towards your toe, it can have a shearing force on your knee. If you are squatting to pick something up, make sure your knee stays more in line with your ankle. Your butt should drop behind you, like you are about to sit on a low stool or chair. PT's will often have you do squats and such and that is fine of course. They often alter them or only do partial squats and lunges compared to what makes up a full squat or lunge, especially if you are going beyond having your upper leg parallel to the floor. Weight lifters and others often do squats to the point their butt touches their heels and this puts a lot of force on the knees.

Offline margret

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Re: What's shearing? How to avoid shearing in the knee?
« Reply #2 on: April 04, 2013, 10:50:26 PM »
Thanks for this explanation! I'm pretty sure I'm shearing my "good" knee with all the one-legged squatting I'm forced to do to sit, but it sounds like I've been treating the operated knee right.