Knee hurts in spinning class

I had a sore right knee not too long ago. It was always fine during the day but it hurt during exercise. My husband lent me his knee brace. Even though it was a little too small for me, it worked well. He said that he had 'runners knee' where the kneecap doesn't stay in the right place during exercise. So, I wore it while I did my spinning and also did some squats to strengthen my leg muscles more. I wore it every time I exercised for about two weeks. Haven't had any troubles since then.

yes, make sure your bike is fit properly. Also, make sure you are keeping the sole of your foot parallel to the floor vs. pointing your toe downwards when you petal, this ensures that you are using you quads and hamstrings rather than you smaller lower leg muscles to constant flex and extend your foot.

hmmm it way be just you're not use to the movement/ form? If you get a chance, ask the instructor to watch your stride and make sure it's nice and fluid. You want to focus on pulling up just as much as you push down as if you were wipping mudd off the bottom of your shoe. This will make sure you engage your hami's and might help with the pain if it's comming from an awkward stride.