Originally Posted by cyclezen

For us to pull a reasonable rabbit out of the hat, there really isn't much usable info.
One of my favorite SNL clips is the 'Sports Announcers Recap' clip, where they gives 'Scores'... you know... 5-2, 2-0, 6-1 ....

.... Quadriceps group usually refers to at least 4 muscles , 3 Vastus and a Rectus... All attach at the knee, Rectus Fem & Vastus Medialis being the one most medial.
Things to consider, besides seat height
Cleat Rotation
saddle fore-aft
gear selection - as in too large gear
extending the days riding could surface an issue not apparent before...
a one-time tweak can be exacerbated into long term condition, if not given an opportunity to 'heal'...
so many things which can contribute to the issue...
things like cleat rotation can be checked...
anytime I do a small 'tweak', I try to think back to when I noticed it occurring, for any possible immediate causes...
check to make sure that any setting I have is not, so how, completely different than what has been my settings range for many years.
if it's only nagging issue and not yet major.... I'll do similar rides, but at a much lower gear and keep the spin in my 'comfort' range...
I'll do these easy rides for at least a week or 2 - better to put yourself in 'hold' than cause more injury which could take you off the bike for a lengthy bit of time...
Ride On
Yuri