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Thread: Knee Flexion

  1. #1
    Senior Member cdale56's Avatar
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    Knee Flexion

    Hello,

    Does anyone know how many degrees of knee flexion one needs to ride a recumbent? Is it the same as an upright?. I can't bend my knee enough to ride anymore and was wondering if a recumbent would be for me?

    Thanks

  2. #2
    Senior Member Retro Grouch's Avatar
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    Could be. I bought a 152 mm crankset for my Rans SWB. That's a full inch shorter than what I was used to. That has made a lot of difference in the necessary range of motion in my knee.

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    Senior Member BlazingPedals's Avatar
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    What retro said. If you can't bend your knee enough, the problem is at the top of the pedal circle. You'll have to make the circle smaller, otherwise if you simply move the top of the circle away from you, you won't be able to reach the bottom of the circle. This is true no matter whether you're riding uprights or recumbents. You can either get shorter cranks, which can come as small as 135mm I think, or you can get crank shorteners (cheaper alternative while you test the concept.)

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    Senior Member oddball's Avatar
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    Look for some Origin8 cranks online. They're cheap, under $50, they look more expensive though. If your bike is newer with some fancy bottom bracket you'll have to buy a traditional square taper BB, shouldn't cost much. You can get them in 155mm length, many people with knee problems find these to be the cure. If you're running a road triple, 130/74 BCD, you should be able to swap your chainrings over.

    Truth is, that if you are having knee problems on your diamond frame you're likely to have the same problem on the 'bent. Could be worse as you can push against the back of the seat and really damage your knees. Try the shorter cranks.
    Last edited by oddball; 07-05-12 at 12:29 AM.

  5. #5
    I am the Snail~! Peter_C's Avatar
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    Hi - to answer your question, lots of ways to lower how much listed above. I have both a replaced hip and a replaced knee, and we looked at angles quite a bit. On a TT 'Rover' with 152mm cranks, my knee flexes to 73 degrees, and my hip closes to 90 degrees. Shorter cranks would indeed lower both of these numbers even more.

    Also, look at the BB height in relation to the seat height - this will affect hips more than knees (but sometimes one follows the other).

    Another possible note? Unless you have actual damage, going into PT *could* be a way to gain more flex?? When a person gets a TKR, they lose flex in both directions, and weeks/months of PT may be required to bring it back (this assumes the joint is capable of the motion. Lastly, have you thought to see an Ortho about this issue?
    Peter_C
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    Hase also provide various solutions.

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    Senior Member Steamer's Avatar
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    Quote Originally Posted by zoxed View Post
    Hase also provide various solutions.
    +1. Their pedal pendulums are a good way to go if the joint movement restriction is fairly significant. They are adjustable too depending on the severity of the problem. And you could chose to use just one on the bad leg and leave the other crank alone as normal if you wanted.

  8. #8
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    Quote Originally Posted by oddball View Post
    Look for some Origin8 cranks online. They're cheap, under $50, they look more expensive though. If your bike is newer with some fancy bottom bracket you'll have to buy a traditional square taper BB, shouldn't cost much. You can get them in 155mm length, many people with knee problems find these to be the cure. If you're running a road triple, 130/74 BCD, you should be able to swap your chainrings over.
    Duuuuuuude!!!! Origin8 155's. Sweet price. Nice tip!
    Rans Stratus XP-AL Sun EZ-1 "Retired" Mountain Biker

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