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knee pain formula.......

 
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dannybaggett
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Joined: 16 Feb 2005
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PostPosted: Thu Sep 23, 2010 10:40 am GMT +0000    Post subject: knee pain formula....... Reply with quote

hey doc nolan......hope all is well w/you & yours. i have a slight pain on the inner/upper portion of left knee......was wondering if you could post that old seat height & fore/aft formula so i can try a couple of things to stop the pain.....it's only a 1-2 on the pain scale.....just bugs me, thats all.
thank you sir, in advance.
danny
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The Bike Doc
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Joined: 08 May 2003
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Location: Corpus Christi and Warda, Texas

PostPosted: Thu Sep 23, 2010 10:03 pm GMT +0000    Post subject: Reply with quote

Here is the posting glad to give it a bump.

The location of the knee pain can be a clue. Pain along the inside of the knee points to the cleats positioning the toes too far out. The feet could also be too far apart and the cleats need to be shifted to the outer aspect of the sole to move the feet in. If the pain is along the outside of the knee the cleats may be positioning the toes in too far. Also the feet could be too close together and the cleats may have to be shifted to the inside of the sole to move the feet further apart. You want the cleats positioned so that your shoe will be clipped in a position that reproduces the natural position your feet prefer to be in. Do this little test: get barefoot and wet the bottom of your feet and walk across a concrete floor in your usual gate. Look back at your foot prints. Note if you are a toe out walker or a toe in walker. Most people are toe out walkers, though a few will be toe in or neutral with toes to the center of the heal strike. Also note how far apart the balls of the feet are from each other. Position your cleats so they reproduce natural direction the toes fall relative to the heal strike and the distance the feet tend to stay apart at the balls when walking. With the shoes off your feet, adjust the cleat position 180 degrees out of phase to the direction you want the toes to go because when you are looking at the cleats the shoes are upside down so if you rotate the cleat right the toe will go left when you flip the shoes over and clip them in. Clip the shoes into the pedal (still no feet in the shoes) and note the position that the shoe naturally falls. Fine tune the cleat position until the shoe falls the way your feet naturally fall when you walk. Do make sure that the cleat release point is at the minimal amount of rotation to allow release because rotating the heal much past 5 degrees to activate release can put undue strain on the knees. Eggbeater pedals do not allow tension adjustment for the release point. This can be a problem as excess tension required to activate release can also cause knee strain. Other clipless pedal bands do allow tension release adjustment.

Other things to consider in knee pain include seat height. A seat that is too low or too far forward can lead to pain in the front of the knee. If you are getting pain to the back of the knee the seat may be too high or too far back. Some clipless pedals can effectively lengthen the seat height relative to standard platform pedals because the shoe is effectively placed lower on the pedal and closer to the axis of rotation and effectively lengthening the distance from the seat to the bottom of the shoe. If the seat is down too low where your knee has more than a 15 degree bend for off road riding and a 10 degree bend for road riding when the pedal is at bottom dead center, you can get undo strain on the knee cap from over flexing the knee at top dead center of your stroke. Also note your pedaling style, if you pedal with your heals down, then you will need to bring your seat down slightly relative to level foot pedaling and if you pedal heals up, toes down, then you will want to have your seat higher than that for a level foot adjustment.

Also look seriously at going with shorter cranks. Mountain bikes come stock with 175 mm cranks. Road bikes come with 172.5 or 170mm cranks. You may benefit from going to 170, 165 or even 155 mm cranks to keep your knee from over flexing at top dead center of pedal rotation. With the shorter cranks you will get the added advantage of improved ground clearance when your cranks are at the bottom of the stroke and they will make it easier to spin smoothly at a high cadence. While on the bike keep the gearing low and the RPM up shooting for cadences above 90 RPM. “The Man,” Lance, used a cadence of 100 to 110 on the long climbs in the mountain stages. Switch to a low gear cluster on the back such as a 12 – 34 for your mountain bike and a 12-27 for your road bike to help spare your knees further.

If you do knee exercises such as extensions, squats and leg curls, bend your knees only 45 degrees to keep the load down on the knee caps. Also keep the weights down. You will have greater benefit with higher reps with lower weights than with low reps with maximal weight.

I hope this helps.

Thanks,
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Paul K. Nolan, MD
AKA: The Bike Doc
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mtnbiker92271
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Joined: 05 Feb 2005
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PostPosted: Sun May 29, 2011 1:25 pm GMT +0000    Post subject: Reply with quote

What such great advice. I recently purchased a 29er and after every ride experiencing pain in both knees. I have never had this before on my 26 inch bike. The pain of walking goes away after a day but the pain of bending down is not leaving. I have lowered my seat slightly and this has helped some but I am now thinking it may be due to the candy pedals I purchased for my 29er.
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The Bike Doc
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Joined: 08 May 2003
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Location: Corpus Christi and Warda, Texas

PostPosted: Mon May 30, 2011 8:51 pm GMT +0000    Post subject: Reply with quote

mtnbiker92271:

If your pedals require too much rotation to uncleate or a higher degree of torque (rotational force) to come on clipped when you want to, that may be causing excess stress on the knees. I find that having more float is desirable but too much can stress the knees if you have to rotated the foot a great deal to deliberately unclip so look at your rotation and force required to come unclipped. The Candy pedals do not let you adjust the tension to come unclipped. So you may want to try using your old pedal and shoe setup to see if that eases your knee pain.

Thanks,
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Paul K. Nolan, MD
AKA: The Bike Doc
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