how long to wait?
last week my knee was hurting a fair amount after a ride, so I decided to take some time off. After 3 days I started riding again on the next easiest gear from what I usually do. Apparently this wasn't long enough since I started having really bad pain in it the next day at work; feels like maybe I pulled a tendon. So now I've been back off the bike for almost a week, and wondering when exactly I should start riding again; I don't want to just reinjure myself.
Ice, stretch, and see a doctor.
You will be amazed at what the first two will get you
Also, check yer bike fit and crank length.
: mountain bike site for women, by women
2013 Ibis Mojo HD
Ditto on the bike fit
Ruling out cycling knee pain caused by a tight IT band, I'd check the bike fit. Make sure your saddle height and fore-aft adjustment is correct. Also check cleat alignment if you ride clipless pedals.
Once you're adjusted, try spinning easier gears for a while.
My deteriorated knees only feel good when I ride often. If the pain continues and you've ruled out the bike, see a doctor. Good luck.