Did you stand up quickly or stand too long. This sounds like it could be a low blood pressure problem; that point just above your knee cap is a big flag for this. POTS is one that has exploded after vaccination. Basically, it is blood pooling in areas of your body, causing blood pressure drop when you change positions quickly, like standing up. To compensate, typically your hear rate rises to compensate. POTS Postural Orthostatic Tachycardia Syndrome...basically hypotension based on position change.

...oh gawd..I need to send Cloudlare a bill for my massive amount of wasted time, just trying to access the Internet. Literally hours to load a saidit page and to make a comment.