Natural Al and HeadHunterSix offer good advice. Get the knee area flexed and warmed up, with a good supply of blood flow in the area. Knee wraps, when not worn too tight, can be helpful. Thought knee warmers might be a better choice. Designed to hold the heat in and allow full ROM. A heating rub could also be applied, if so than again, do not keep the wrap/warmer too tight. Streaching out and warming up the hams is also a good idea, they can affect the function of the knees. Both work with one another when doing most leg movements. You want a fairly even muscle balance when doing any exercise.
Knees can be very tricky. Trouble is, is that if one minor thing goes wrong, that can start a chain reaction to something more serious. Couple of things that come to mind. 1) If that knee tightness goes along with a slight/moderate burning feeling, than that may, or may not, suggest the start of a tendon tear. 2)Wonder if the knee cap is loose/floating?
You could take a week (or two) off of any direct exercise that requires a 90 degree bend in the knee joint; squats, hacks, leg presses, etc. Though I always thought that leg extensions were a good way to increase strength and knee health, if not extended beyond the normal point of top contraction, some recent White Papers have suggested the opposite. Who know now a days, next week it might be back to it being a good exercise. So, in good conscious, I cound not suggest doing them at the moment. But you can be the only judge of that. Seeing a doctor is always a major option if results are slow, or not at all, with your knee health. Good Luck.
