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  1. #1
    Member bubber's Avatar
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    How to measure knee angles

    I am trying to measure the angle of my knee at the 12, 3, 6, and 9 o'clock crank arm positions by laying out lines on photographs take from the side. It seems to me that the line for the lower leg should run up the shin because the bone is right there. However, where should I put the line for the upper leg? The top and bottom of the thigh seem inappropriate because of the contours of the big thigh muscles, and it is not easy for those ignorant of human anatomy to guess exactly where the thighbone is. None of the cycling books I have read give instructions on exactly how to measure the angles they refer to. Any suggestions?
    Leave no one behind -- eat your dead.

  2. #2
    Senior Member late's Avatar
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    Lay a yardstick along the side of your thigh. Hold it in the middle, and there's your reference. Basically, you want a little bend at the bottom of the stroke. Say 11 and 6?

  3. #3
    . . . rosebud . . . Diggy18's Avatar
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    I read of a way to measure seat hight without having to measure any angle. Put the forward crank parallel to your seatpost (which will not be 6 o'clock, but maybe 7 or 7:30), and lock your knee. Now your foot, in the normal position on the pedal, should be parallel to the floor. This will give you the requisite knee angle when the pedal is at 6.

    Of course, this doesn't help with the 3 o'clock position I suppose.

  4. #4
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    You could get a goniometer and have someone measure you that way. It's pretty cheap, and it's pretty easy to get one.

    RevMaster makes a nice one, but I didn't see it on the website. But go to this link and ask them how you can order one:

    http://www.lemondfitness.com/support/index.html

    Make sure they include directions. You really have to measure your leg angle a specific way. I have one, I use it for everyone I set up, and it does definitely work, and they are fit comfortably on the bike once I've measured them up.

    Koffee

  5. #5
    Senior Member JavaMan's Avatar
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    For the three pivot points I would use:

    1. Ankle, the bone that sticks out to the side
    2. Knee, just behind the kneecap
    3. Hip, find it by feel

    If you lay on your side on a hard floor, these will be the contact points. If they don't show up in the photo, mark them with tape or something.

    I'm pretty content with the slightly bent leg at 6:00 concept myself.
    Tom

  6. #6
    Member bubber's Avatar
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    Goniometer. That is a new word to use tomorrow. Anyway, I did a google search on "goniometer" and got a number of hits. The Lemond web site apparently sells them as part of a $250 kit -- a bit more than I wanted to spend. Other medical sites carry small gonimeters for measuring range of motion in fingers and such. JavaMan was headed in the same direction as me, namely: what are the reference points for the angle measurement. If I know that, I can kludge something together for infrequent measurements on myself. This web site

    http://www.physsportsmed.com/issues/...mar/kronpa.htm

    gives the following:

    "To measure knee angle precisely, center the goniometer at the lateral femoral condyle, and point the ends toward the greater trochanter at the hip and the lateral malleolus at the ankle."

    The hip (greater trochanter) and ankle (malleous) are the same reference points suggested by JavaMan. With the hip, the lateral femoral condyle (epicondyle in my anatomy book) form one side of the angle. The only missing reference point is at the top of the lower leg. How about the lateral condyle of the tibia? If this is the other reference point, I can put white dots on each point, get on the bike, take a digital picture, connect the dots, and use a protractor to measure the angle.
    Leave no one behind -- eat your dead.

  7. #7
    Member bubber's Avatar
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    How does this look? I measure a knee angle of 28 degrees using the greater trochanter, femoral condyle, and lateral malleolus.
    Leave no one behind -- eat your dead.

  8. #8
    Senior Member JavaMan's Avatar
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    Quote Originally Posted by bubber
    How does this look? I measure a knee angle of 28 degrees using the greater trochanter, femoral condyle, and lateral malleolus.
    It looks great (the angle, not your leg!). But how does it feel? That's the important thing to me. I just lowered my seat about .3 inch and find it is more comfortable for spinning the higher rpms when riding in a fast group. Judging from your picture, I would say my seat is a little lower than yours.
    Tom

  9. #9
    Member bubber's Avatar
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    It feels OK, but I have been struggling with patellar tendonitis a bit lately. A number of references I have looked at recommend that one with this problem should set the seat so that the leg angle is around 25 degrees. This whole exercise was an effort to see where I stood with respect to this recommended knee angle. Thanks for the help.
    Leave no one behind -- eat your dead.

  10. #10
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    I've always used the slight knee flex at 6:00 as a base point and make minor adjustments until I'm at the verge of rocking at high cadence.

    I've noticed a wide range of ankle angle amongst riders. Some almost ride with toes pointed down while others have a more horizontal foot position - you can see this difference between Lance and Ullrich. In both cases there is varying amounts of ankle flexing during the stroke. Do any of the newer methods account for this persumably natural difference?

  11. #11
    Refrigerator Raider Hater fordmanvt's Avatar
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    I know I'm digging up a really old post, but the simple solution is to measure distance from ankle to hip.

    Use your knee as the third point in a triangle. Then you will automatically know the length of all three sides since your calf and thigh are always the same length, hence all three angles are known. Although you only care about knee angle, the other two are meaningless in the real world.

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