Sore knees - crank length?

Lobbydosser

Hi

My girlfriend has been riding her road bike for a year now and has pain in her knees. She suspects it's either her cleat position or crank length. Her current cranks are 170mm and she is just over 5' 5"

When she bought her current bike she had a complementary bike fit but wasn't that impressed at the time and is considering another elsewhere.

Any suggestions out there?

Cheers.

xcMuttley

It could be a number of things unfortunately, The seatpost may be to high which hyper-extends the leg which will obviously hurt her knees. Or it could be too low which makes her legs "kick" out to the side which will also hurt the knees after a long ride. Try Moving the seatpost so that her legs are almost fully extended at the bottom of the pedal stroke, just so that there is still a slight bend in the knee.
Another possibility is that she is not positioned correctly over the pedals, moving the saddle back/forth on the rails will fix this. + cleat position. Apart from trial and error the best thing to do would be to have another bike fit done by a different shop? But obviously the trial and error option is a lot cheaper! Hope that give you some help

MichaelW

A 170mm crank is probably within bounds for a rider of that size but some riders prefer a shorter rather than longer crank. See Peter White bike fitting advice.
In addition to saddle and cleat position, check that the cranks are straight and well aligned. Damaged cranks can pivot the pedal spindle on each rotation.

Wacky Racer

I'd stump up for a proper bike fit personally. Knee pain could be caused by a significant number of things within the bike itself, but it could be an underlying problem that has become evident since cycling. There will be plenty of well meaning folk on here who can point you in a variety of directions, some will be good advice, much will be contradictory, some will be poor advice.

I have been plagued by knee problems for a few years now, none of which has been caused by cycling. To put my mind at rest I paid for a good bike fit. The knee specialist takes care of the rest. Knee problems are often complex, it's worth getting good advice.