Knackers for knee's
It took about ten years to get all the knee carteledge regrown, with out surgery, letting the body naturally replace it. That, along with standing at a workbench. I worked standing, in and about Outboard boat engines. I fixed them for most of twenty plus years really which made my legs into stretched rubber band muscles. It was painful to sit crosslegged for the first three years of Karate and seiza didn't become possible until my third year of Aikido ... damn legs wouldn't bend that way. Old and stiff.
There are simple strengtening exercises, like lifting your leg slightly while sitting and extend your foot until it is like a horizontal kick. About fifty times per leg, until you are tired or any pains begin. Lower/lesser repetitions when you begin, until you can literally do a sitting kick as face level.
If your knees are really bad, then simply sliding your foot on the floor until your leg is straight will begin to stretch and strengthen the muscles around the injury.
I think I spent two years putting ice/heat on my knees before I started the exercise method that finally eliminated much of the pain. It is not an easy quick process. Wearing two leg supports helped when one knee was weak. Especially, get good foot supports that help your arch and back ... it's bad enough to have barking knee's.
Never be afraid to sit out practice if it is too much, and I don't mean seiza or crosslegged, but in a chair off the mat.
One morning you will get up and get going with any supports and wonder why you forgot them?
Exercise, diet, and check with your doctor about the effects of a water pill that takes water out of the joints. I can't remember what it is called, but when I started it for water imbalance in my ears for Meniere's, it cured the clicking, clacking almost like I was getting younger. The seiza ... that, as I say, took me over three years of slow stretching.
Start before you are forty six, it should come a lot easier, quicker. Cheers.