About 5 weeks ago while riding my bike, I experienced a very sharp sudden/acute pain in my knee. The pain seemed to hit at the top of the patella on bike side of my knee.(inside knee) I am still not 100% pain free and want to ensure my bike is set up properly in the hopes of preventing this from ever happening again.
My bike is a 56cm Trek 2100 with a 170mm crank, Shimano Ultegra pedals, Italia Flite saddle, and 100mm bontrager stem. I’ve since had my cleats professionally positioned. I’m 5’10" tall. The measurement from the top of my femur to floor is 35.25". Inseam is 31.5". From what I have read about preventing knee pain, proper fore/aft saddle location is very important. I have also read that proper crank length should be roughly 18.5% of the “top of femur to floor” measurement. So femur to floor says I should be using a 165mm crank.
I use the “plumb bob” method of establishing proper fore/aft saddle position. (string placed at front of knee and bisects the pedal’s axle) By using this method, the saddle is positioned fairly far back to the point that I am stretched out pretty far in order to reach the handlebars. If I go with a 165mm crank I would be stretched out even further. So, I am assuming that means going with a shorter stem to straighten me up a bit. How much shorter Im not sure and assume it will depend on how much I have to adjust for the shorter crank.
Here’s my question. From the info provided above, am I on the correct path to properly setup my bike to prevent further knee injury? I’d hate to go buy a new crank and stem only to find out later that this wasn’t needed or I went shorter when I should have gone longer. Any suggestions would be greatly appreciated.
Knee pain often indicates that the saddle is too low.
I’m 6 ft tall, 31 inch inseam and ride with 172.5mm cranks with no problems whatsoever. Using a forward seat post, my saddle is pushed forward to where it’s only a few inches behind the bottom bracket on my road bike.
Same thing happened with me. Hadn’t been on the bike in a while then went for a ride and the next day had a pain on the inside of my knee - turns out someone else had been on my bike moved the seat position (lower) and hadn’t put it back. I ended up moving it higher by about 5mm or something - knee pain gone.
Don’t take the “string bisecting the pedal” method too religiously. Slowman does a whole article about this, but if you think about the geometric relationship between your pedal axle, knee, and seat, then entire group could remain fixed with respect to each other, but rotated around the bottom bracket, to give you any distance you want between where your string falls down and the pedal axle. So, depending on your seat tube angles (effective), the string method may or may not make sense. It makes more sense for “traditional” (73 degree) seat tubes, with steep tri-geometry, you should see the string moving forward as you rotate the points mentioned around the bottom bracket to get the steep seat angle.
Have your fit evaluated, post your picture here, or just compares some of the other posts to your own picture. If you are in the “ballpark”, then you probably just need to experiment to find what works. I’ve had knee pain (back outside) and tried LeWedge’s, different seat positions, crank lengths, and different pedals, but it eventually came down to finding some good ITB stretches that solved the problem.