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Adaptive Cycling: Handcycles, Amputee Adaptation, Visual Impairment, and Other Needs Have a need for adaptive equipment to ride to compensate for a disability or loss of limb or function? This area is for discussion among those of us in the cycling world that are coming back from traumatic circumstances and tell the world, "No, you are not going to beat me down!"

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Old 07-06-17, 02:32 PM   #1
Ninagb
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Limited Knee Flexion

I've loss some knee flexion after a knee replacement. I'm unable to pedal normally with that leg. I point my toe and am able to get around but it's quite uncomfortable. I've also raised my seat a bit more than it should be. I'm looking for any ideas I might try or adaptions to my bike that might help me pedal without pointing my foot/toe to get around.
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Old 07-06-17, 03:16 PM   #2
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A few ideas: shorter cranks, Ride2 crank shorteners, a mid-foot riding position...

Maybe, have the knee checked out. There could be something wrong with it that needs to be looked into.
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Old 07-06-17, 03:18 PM   #3
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How much bend do you have?
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Old 07-06-17, 03:59 PM   #4
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Short crank arms are the standard fix for limited knee ROM. How long are your current cranks?

Road cranks are often available as short as 165mm, with some companies (i.e. Spécialtiés TA) offer arms as short as 155mm. If you need them even shorter, BMX crank arms are available down to 110mm, but might need some tweaking to work on a road bike.

If you're working with a physical therapist post-surgery, they can help determine how short you need to go.
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Old 07-13-17, 05:43 AM   #5
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Thanks

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Originally Posted by Ninagb View Post
I've loss some knee flexion after a knee replacement. I'm unable to pedal normally with that leg. I point my toe and am able to get around but it's quite uncomfortable. I've also raised my seat a bit more than it should be. I'm looking for any ideas I might try or adaptions to my bike that might help me pedal without pointing my foot/toe to get around.
Thanks for the ideas. I'm having a shorter crank put on today. Can't wait to see how much difference it makes.
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Old 07-13-17, 10:37 AM   #6
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What length are you going with and how many degrees of bend do you have to work with?
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Old 07-15-17, 06:09 PM   #7
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IMO - your best bet is to work with a physical therapist to reestablish more knee movement. The usual issue isn't lack of range of motion per se, but range of motion with load. That can often be remedied by using lower gears, possibly combined with a shorter crank on one side.

But the long term goal should be to get the range back, and that should trump being able to ride the bike more easily in the short term.

When I first started in the bicycle bi almost 50 years ago, I used to work with a surgeon who repaired knees for top athletes. This was before the scope, so it was heavy surgery with a long recovery process. He believed in using bicycling as part of the recovery process, and I'd set up bikes with limited low gearing so they couldn't work harder than intended, and fit guys who came into the store on crutches or in a wheel chair, so they could ride a bike out. But the key was controlled movement at low low load, and as they improved, he'd send them back for me to adjust the gearing to allow a bit more load.

BTW - depending on the details, you might get by by raising the saddle higher than normal, so the knee's flex cycle, is shifted to the straighter end of the range. This will work, but you'll be reaching, and might get excessive rocking at the hip, so it may not be well suited for longer distances. It may be worth a shot, though.
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Old 07-22-17, 04:29 AM   #8
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My total knee replacement went poorly and hurts at 95 degrees. I just moved to 127 mm cranks on my town tourer and its working well enough. They're short but you can compensate with a wider range cluster.

I'm looking at revision surgery in the winter. We're going to shave my patella down, as it appears to be a couple of mms thicker than normal and could be the source of restriction. Fingers crossed.
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Old 07-22-17, 10:43 AM   #9
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My total knee replacement went poorly and hurts at 95 degrees. I just moved to 127 mm cranks on my town tourer and its working well enough. They're short but you can compensate with a wider range cluster.

I'm looking at revision surgery in the winter. We're going to shave my patella down, as it appears to be a couple of mms thicker than normal and could be the source of restriction. Fingers crossed.
Based on your numbers and going with 120° as what is required for no issues (not positive about this number but, using it as what is needed to accommodate what has become the industry standard of 175 mm cranks), I'm guessing that ~115° might be what's needed to feel comfortable on 165 mm cranks... Just playing with numbers as there is no information that I have been able to find on this issue. I have read about an implant that was designed specifically to accommodate a greater ROM but the results seemed to be inconclusive. Dr's seem pretty happy with achieving at least 90° for their patients and this amount certainly increases the quality of life for any in need of a new knee but that amount is limiting when it comes to cycling. Seems like shooting for at least 145 mm cranks should be a reasonable objective --e.g., by the math above, getting to ~105°.

Last edited by McBTC; 07-22-17 at 10:56 AM.
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Old 07-22-17, 12:19 PM   #10
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Based on your numbers and going with 120° as what is required for no issues (not positive about this number but, using it as what is needed to accommodate what has become the industry standard of 175 mm cranks), I'm guessing that ~115° might be what's needed to feel comfortable on 165 mm cranks... Just playing with numbers as there is no information that I have been able to find on this issue. I have read about an implant that was designed specifically to accommodate a greater ROM but the results seemed to be inconclusive. Dr's seem pretty happy with achieving at least 90° for their patients and this amount certainly increases the quality of life for any in need of a new knee but that amount is limiting when it comes to cycling. Seems like shooting for at least 145 mm cranks should be a reasonable objective --e.g., by the math above, getting to ~105°.
I think your numbers are good, at least a match for my physiology. I was riding 138's for awhile but swelling, stiffness and a little pain would happen after a slow 15 km ride. Early on, I optimistically bought a 145mm Cobb crankset for my good road bike but I know I'm not going to be able to put them to use until I claw back that extra 10 degrees or so. Even then, I think platform pedals will always be a part of my riding experience from now on.
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Old 07-24-17, 02:07 PM   #11
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Shorter Cranks

I went to 55 mm cranks. This has worked well. I am comfortable riding and can stay in my seat without rocking.
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A few ideas: shorter cranks, Ride2 crank shorteners, a mid-foot riding position...

Maybe, have the knee checked out. There could be something wrong with it that needs to be looked into.
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Old 07-24-17, 02:10 PM   #12
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I went with 55mm. Riding is great again.
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