My left knee aches most of the time, after a hard kneecap/Tarmac interface. It often feels like my leg wants to hinge sideways, if I put too much weight on it. Been to the doc, who basically said I've got to live with it, or else it's highly invasive surgery, with no guarantee that there would be any significant improvement.
It's nagging at me now, and I'm sprawled on the couch with my legs up, but it's still uncomfortable.
Getting older doesn't help matters, for sure.
Riding doesn't aggravate it, but I'm afraid to ride too much, especially in winter, in case the bike does the same as last time; both tyres went sideways at walking speed having just turned onto a shared-use cycle path, with no warning.
Good thing my helmet stopped my skull hitting the ground, too, scuffed the visor, and made my ears ring, and grazed my face.