Q-Factor and Knee Pain

roubaixtom

Recently I have changed my cranks from 105 5800 170mm 50/34 to Ultegra 6800 170mm 50/34. After a few rides I have developed knee pain mainly on my left inside/front. I have suffered from knee pain for a while whoever not for about a year.

The Q factor of the 105 cranks is 146mm and the Ultegra 6800 is 146.6mm. This means there is a 6mm difference, 3mm on each side.

Could this be the cause of the knee pain that has suddenly appeared?

mfin

Have you mis-typed? 146 to 146.6 is a difference of 0.6mm, or 0.3mm each side which is nothing.

(If they are actually 3mm further out on each side you could move the cleats 3mm towards the outside of the shoe to negate it).

Personally I doubt it's anything to do with the Q, more likely fluke.

sungod

pain in that position can be caused by lack of sufficient arch support (and/or umpteen other things)

two simple indicators that you should consider looking closer at what's going on...
- when walking barefoot, as your foot touches down does the heel 'roll' inwards?
- when cycling, do your knees move up-down in a vertical plane parallel to the top tube, or does one or both also move side to side?

heel rolling is a classic sign that arch support may be helpful, knee(s) going in-out is more complex but arch support and/or wedges may help, but everyone is different, some people naturally do these things without it being a problem for them