Artificial knees

[destination]

Recently went shopping around for a bike for a person with artificial knee's.  We tried our best to hold off
as long as we could in order to do a good search of all possibilities. Sunshine and warm weather did not help the situation (of holding off)

[Tourista829]

Would he consider an electric bike? I rode one in Ft. Lauderdale, last month, from a German company that was very light and had good assist. It also had good range and he could ride it without the assist unless he needed it. If interested, I will give you the info. 

[destination]

Will get back to you.

[rvklassen]

So I'm a bit puzzled as to the constraints here.  By "artificial" are you talking more than the standard "knee replacement" that appears to be in my future (but being delayed as long as possible), or something more?

If it is "just" a knee replacement, I would think all you need is something with low gears, and the will to use them.

[destination]

As far as I know, we are talking standard knee replacement. If I understand it correctly there are steel plates involved. If this person were to fall down on ie: cement, the bone in between the steel plate and the cement would more then likely crush the bone. Or, at least, that is what I have been told.

I do know that this person cannot kneel due to a "pin" (sort of speaking) that one would feel upon kneeling and is painful. Its not really a pin, its an attachment, but, it is not a comfortable attachment in the kneeling position.

The next thing I learned is that the replacements only last so long. So, my question is, will biking shorten the life of the replacement?  

We both are certainly learning as we go. And, this person definitely has the will to keep moving forward.

[Spokey]

I don't know about knee replacements (although I may have to learn sometime soon myself but I'm still working on therapy).  I have had several members of my family with hip replacements.  When I looked at those, i found there were several kinds.  Some were longer lasting but no good for athletically inclined while others stood up to the abuse but needed to be replaced sooner.  



Perhaps it is the same with knees and this would be good to know before getting the surgery.

[whittierider]

I don't know how knee replacements and hip replacements compare, but Floyd Landis had a new metal ball put in his hip joint and went back to professional-level bike racing.  See http://velonews.competitor.com/2006/09/news/landis-surgery-a-success-docs-say-return-to-sport-likely_10941.

And, ahem-- theres no apostophe in words like "knees" that are just plural (meaning more than one), unless they're also possessive, meaning that something belongs or relates to them, like "the girls' team" (which has the apostrophe after the "s" because it's both plural and possessive).  This is 3rd-grade stuff.

[vanvalks]

As far as knee replacements go, there are usually four pieces:  1) a metal piece that is glued to the femur(thigh bone) 2) a plastic tray that is roughly 3/16" thick 3) a metal piece that is glued to the tibia (the big bone of the lower leg) and 4) a plastic button that is glued to the underside of the kneecap.  The plastic tray sits between the two metal pieces.  The rounded end of the femoral component rides in a dished out area in the plastic tray, which is locked into the tibial component.  In some knees there is an upward projecting metal stud at the back of the replacement which serves as a lock to keep the joint from bending the wrong way, but usually the posterior ligaments are left intact, and they do that job.  Riding a bike will put very little wear on a new knee joint--what wears them out is being overweight.  The male human knee, regardless of how tall the person is, is just not large enough to handle more than 200-250 pounds.  It is a case of too many pounds per square inch of pressure.  With women, the upper limit is probably nearer to 180-220 because of the smaller surface area of the joint.   If one wants their new joint to last a long time, the best thing to do is to get the weight off, and non-weight bearing exercise like cycling is a good way to accomplish that goal

Bob (retired MD)

[destination]

Vanvalks: THANK YOU!!!

Whittierider: Thank you for the correction. From about the third grade on, it was a matter of survival for me and concentrating on learning was no longer a priority. Is that why I cling to third grade level material? :-)
Ok, I corrected mine...  I cant correct the others.

[rvklassen]

I think you may have misunderstood my phrase "the will to use them".  This is as opposed to the desire to push it in higher gears.  Generally, as long as the gearing is low enough for a high (which means anywhere upwards of 80 something, but could mean 100+, depending on the person), cadence, bicycling is easier on the knees than walking, which in itself is easier than running or jogging. 

Beyond that I would strongly recommend against using SPD-style clipless pedals.  I've not used Speedplay Frogs, but I understand that they may be easy enough to get in and out of as to cause no knee stress.  But I'd want to verify that.  I personally have SPDs, and had to switch one of them out for a month or two when recovering from a knee injury a couple of years back.

As far as weight being the culprit for knee failure, sometimes.  Yes most very heavy folks have bad knees.  It is also the case that a disproportionately high fraction of tall ones do, without being overweight.  As I mentioned, I'm planning/hoping to avoid knee replacement for many years to come, but being tall, and not at all overweight (BMI 21), I do have issues.  Exercise helps.  Certain activities make it worse.  It has much more to do with my height than my weight.

[destination]

"I think you may have misunderstood my phrase "the will to use them".  This is as opposed to the desire to push it in higher gears.  Generally, as long as the gearing is low enough for a high (which means anywhere upwards of 80 something, but could mean 100+, depending on the person), cadence, bicycling is easier on the knees than walking, which in itself is easier than running or jogging."

Yes, I certainly did misunderstand you. The gear thing is going to take me a while.   

[vanvalks]

I certainly didn't mean to imply that being overweight was the only cause--merely one of the most common.  If you're tall, you put more stress on the knee joint because there is a longer lever arm--think of the knee bent to 90 degrees.  A light weight on the end of a long femur puts the same stress on the joint as a heavy weight on a short femur.  The total pressure on the cartilage in the knee can exceed 2,000 psi when a heavy person does a deep knee bend.  There just aren't many materials around that can stand up to that sort of repetitive pressure for many years.  Running or any other trauma can damage the cartilage and start a positive feedback system of more damage causing more loose particles, which causes more damge, and so on.  The problem is that cartilage grows so slowly, once damage gets started, it is hard to reverse the positive feedback cycle 

Bob

[mknotts]

I had a total knee replacement about 5 years ago. I have found that a recumbent tricycle is the perfect answer for me. Since I have no kneecap on that leg I cannot stand on pedals anyway, so I just put mountain gearing on my Catrike and never looked back. In 2007 I rode the trike from Marietta, GA to Oak Harbor, WN for my 50-year high school class reunion and had no knee trouble at all. See www.MerlesMilesForMS.com if you are interested in reading my daily trip log.
I have the "normal" 27 speeds plus a SRAM dual drive hub that gives me a total of 81 gears with a very wide range. I can ride up almost anything that I can walk up.
Since using a tricycle means that I don't fall over, clipless pedals work great for me.

Merle

[CraftGeek]

Something else to consider is replacing the standard peddle cranks with shortened ones. I have a diminished left knee (tore the ACL and PCL years ago) and have found that 153 mm crank arm length works well for me.
The reason it helps (I think) is that the knee does not need to bend at such an acute angle it the top of every stroke. Also, when you start the power portion of the stroke your knee is a bit less bent and your mussels are not as stretched.

I've just begun riding with shortened cranks and it seems better for my knee.