That’s not at all true about knees, for the record. They’re actually notoriously slow healing, and you’ll often experience pain for several months or years after an injury is nominally repaired.
I tore some ligaments in my knee in my early 30s (tripping off a curb in a grocery store parking lot, of all things), then reinjured the same knee almost exactly a year to the day after that (tripping in the backyard while raking), and then again almost exactly two years after that (tripping over the raised edge of an irregular sidewalk while walking the dog). Yes, I am very clumsy.
I saw very good specialists and did a few rounds with a fantastic physical therapist, and though it’s been theorized that I might have been left with a rough area on the back of my kneecap (very hard to see in any type of scan), there’s no evidence of any lasting damage. I was still, ~12-15 years on, in a spectacular amount of pain kneeling on the sofa tonight to fish a dirty baby bottle out from underneath.
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