Does it make a difference?
I have had my cleats repositioned from fwd to back, and there wasn’t any difference in stress on my knees. YRMV.
Seat HEIGHT matters more than cleat for/aft position for knee issues. There is a great deal of debate though about more or less FLOAT in the pedal regarding knee issues (knee issues being a pretty vague statement as there is a big difference in suffering from patellar tendonitis, iliotibial band syndrome and osteoarthritis for example).
Does it make a difference?
Cleat position probably makes little difference. In fact, at any given power and cadence there isn’t much that can be done, I suspect, to dramatically change knee stresses. One thing I can think of that might change these stresses a little would be saddle height and crank length, both of which affect how much the knee bends. Bend it less would probably mean less peak stress at any given power and cadence.
Chondromalacia, stage II. It may or may not be the source of a nagging inflammed feeling that has kept me off the bike for a long time (1 ride every 2-4 weeks, just to see if it’s better… never is). Kneecap pops a lot, loudly. Stuff like that. No question, riding irritates it. I’ve loaded up the Q-rings, can’t really tell if it’s less stressful.
Frank, your point makes sense to me.
Chondromalacia, stage II. It may or may not be the source of a nagging inflammed feeling that has kept me off the bike for a long time (1 ride every 2-4 weeks, just to see if it’s better… never is). Kneecap pops a lot, loudly. Stuff like that. No question, riding irritates it. I’ve loaded up the Q-rings, can’t really tell if it’s less stressful.
Frank, your point makes sense to me.
How could I have forgotten this???!!! One other thing that can reduce knee stress is PowerCranks (or changing your pedaling style from masher to “spinner”). At any given power, the more you unweight or pull up on the backstroke the less you have to push on the downstroke.
You’re losing your edge, Frank. Can’t believe you let that one almost slip. 
I’m a natural masher – 80rpm kinda guy.
Recall our brief exchange on this a few months ago. One of the orthos I’ve seen (Ting) thought they would be worse for my knee. When I pull up against resistance, my knee “loads up” quickly and “needs” to crack. You argued that a hamstring/hip contraction can’t put pressure on the kneecap. I merely relayed his opinion.
I was going to try PCs again a couple months back and my heels kept clipping/brushing the crank arms. They’re fatter than my Campy and SRM crank arms. That was bad news for the bad knee in just minutes. Stranglely, I didn’t have that problem before during my previous trial (~2-3 months - all that did was worsen a still-nagging hamstring problem). One interesting thing from that experiment, after 6 months off, my PC spin was still just fine. So I wonder if when I mash, I’m still un-weighting the pedal naturally anyway.
Maybe I’ll try again soon. Could be that I used different shoes. I forget.
You’re losing your edge, Frank. Can’t believe you let that one almost slip.
I’m a natural masher – 80rpm kinda guy.
Recall our brief exchange on this a few months ago. One of the orthos I’ve seen (Ting) thought they would be worse for my knee. When I pull up against resistance, my knee “loads up” quickly and “needs” to crack. You argued that a hamstring/hip contraction can’t put pressure on the kneecap. I merely relayed his opinion.
I was going to try PCs again a couple months back and my heels kept clipping/brushing the crank arms. They’re fatter than my Campy and SRM crank arms. That was bad news for the bad knee in just minutes. Stranglely, I didn’t have that problem before during my previous trial (~2-3 months - all that did was worsen a still-nagging hamstring problem). One interesting thing from that experiment, after 6 months off, my PC spin was still just fine. So I wonder if when I mash, I’m still un-weighting the pedal naturally anyway.
Maybe I’ll try again soon. Could be that I used different shoes. I forget.
Most PC users do not pull up against resistance on the upstroke, they simply unweight plus a few ounces. You have ridden them so you know this.
The cranks are they way they are to accommodate the clutch, not much we can do about it. That means a few of you do hit your ankles. Most people learn to keep their feet straight, so it is another thing we correct, but some are mechanically unable to do so. They need some pedal extensions to move their foot out a little bit. Our long adjustable cranks do that by themselves but all the others don’t. Consider moving the foot out with some pedal extensions if you try them again.
People do tend to “keep the ability” for substantial periods after adaptation. But, my guess is when on regular cranks you are just unweighting a little better than before but not completely unweighting as required by PC’s.
I’ll tell you after I finish biomechanics (one of my classes this semester! and very cool, is kinesiology + physics, lots of fun).
Hope you’re well — fish kisses!
tc
Love your enthusiasm - it is catching.
But, I TEACH biomechanics and I don’t really know the answer! (shhh … don’t tell anyone)
You are a professor AND a doctor? What college do you teach at?
Like most classes I enjoy reading the book and studying it but the class part of it is boring. (Is that why most people just skip classes? 
I’ll tell you after I finish biomechanics (one of my classes this semester! and very cool, is kinesiology + physics, lots of fun).
Hope you’re well — fish kisses!
tc
Might not matter. I slid 'am all the way back (about 5-7mm) and didn’t notice any difference. Having googled the cr#p out of the subject, I found stuff that said you use your quads and glutes more that way, which puts MORE load on the patella. Well peachy. And then I think about if you did the reverse, would it matter?
At any given power, the more you unweight or pull up on the backstroke the less you have to push on the downstroke.
What competitive rider would want to push down less on the downstroke. You are correct, although it would have been more correct if you had said “the more you unweight or pull up on the backstroke the less you are able to push on the downstroke”, so you finally admit it, and this is why Coyle’s scientific fact on circular v mashing is true. This explains why PC style pedaling cannot increase overall power output. The competitive rider seeks to get most power from the successful combination of both down and up areas of the pedaling circle.
At any given power, the more you unweight or pull up on the backstroke the less you have to push on the downstroke.
What competitive rider would want to push down less on the downstroke. You are correct, although it would have been more correct if you had said “the more you unweight or pull up on the backstroke the less you are able to push on the downstroke”, so you finally admit it, and this is why Coyle’s scientific fact on circular v mashing is true. This explains why PC style pedaling cannot increase overall power output. The competitive rider seeks to get most power from the successful combination of both down and up areas of the pedaling circle.
If you say so.
I dislocated my left kneecap and had historically weak VMO that has resulted in major kneecap mobility in the past. I have successfully resolved through the following:
Major glute strengthening program (including abductors)
changing biomechanics to utilize more glutes less quad (which seems to activate VMO significantly)
Higher than “normal” seat position with slightly toe down pedaling style
Major bodywork to relax quad (not IT band) and TFL
it took about six months to show much progress, and my bike/run is about the same… but my kneecap stays where its supposed to.
Don’t know what you’ve done but thats what has worked for me. good luck!
I dislocated my left kneecap and had historically weak VMO that has resulted in major kneecap mobility in the past. I have successfully resolved through the following:
Major glute strengthening program (including abductors)
changing biomechanics to utilize more glutes less quad (which seems to activate VMO significantly)
Higher than “normal” seat position with slightly toe down pedaling style
Major bodywork to relax quad (not IT band) and TFL
it took about six months to show much progress, and my bike/run is about the same… but my kneecap stays where its supposed to.
Don’t know what you’ve done but thats what has worked for me. good luck!
Interesting… I’ve done exactly all of that (although modest glute / abductor effort that I’m stepping up now) plus:
- 5 Synvisc/Supartz injections
- Q-rings on the bike
- Bongo board work
- Massive quad stretching
- $2000 in physical therapy (my share after insurance)
- Yoga
- Praying to God
- Crying
- Complaining
The glute work was what really tipped things over the edge for me. I couldn’t really get my VMO’s to activate prior to that, although, the compex muscle stimulators work decently as well, but hard to get access too one unless you buy it.
I’m moving over to rotor cranks myself on a TT bike I’m building up.
Seems like we’ve been reading the same articles on the interweb.
I forgot compex. I have a similar Euro product. Did lots of that, too.
I have to hope that 1) Frank is right (previous thread) that there’s something nerve-related that can be fixed and/or 2) it just magically heals… after a year already, and months of inactivity. Riiiiiiiiight.