Why Does Riding Hills Hurt My Knees?

Question: I’m a MTB racer who purchased a new road bike last summer and have trained hard on it, especially on short steep hills. This has made a huge performance difference in my MTB riding, but do you think pushing the bigger gears is why my knee hurts? — Paul Y.

Coach Fred Matheny Replies: It’s hard to be certain, but you might look at these variables:

Are you sure your position on the mountain bike and road bike is the same? Besides seat height, you need to check setback. Sometimes a saddle that’s too far back on the rails, putting you excessively rearward of the bottom bracket, can cause knee problems.
Are your cleats set with the same amount of toe-out or toe-in on both sets of shoes and pedals? Even if you use the same shoes on both bikes, the narrower bottom bracket of the road machine’s double crankset changes your effective foot angle and can cause knee injury.
Do the pedals on both bikes allow the same amount of float (foot rotation)?

I bet you’re attacking those hills in a bigger gear than you’d use for a similar grade on your mountain bike. Due to the uneven nature of singletrack, you tend to use a lower gear and spin up so you don’t lose momentum when you encounter an obstacle.

But on a road bike, you can hunker down in a big gear and crank hard. That’s a sure cause of knee problems if you aren’t accustomed to it.