This may sound like a variation on day 1 when I was grateful for my lungs being OK now. Because today I'm thankful for decent joints: knees, ankles, hands etc.
A co-worker who is a couple of years younger than I am has to ice her knee constantly. She stays very active but has issues with that knee and hasn't taken the time to let her knee heal up. Now you could argue that her approach is pretty short-sighted and I would completely agree with you. Nevertheless, she believes she can power on through and she's also positive this is just a congenital thing, rather like her bunions.
Fortunately for me, I don't have any congenital joint issues (nor do I have bunions). Any time I've had problems with anything, usually my ankles, it's because of an injury. When I first returned to running in 2006, I had some pain in my knee but I changed my shoes to minimalist shoes and I also revamped how I run and poof! No more pain.
Watching this co-worker walk is almost disturbing because she lurches from side to side, sort of how I think zombies walk. I did a quick bit of Googling and holy cow there are a lot of different types of abnormal gaits out there (here's a link to a description of eight of them)! I had no idea, nor do I know what, if any, kind of disorder she might have. I suspect it's because her knee is so unstable and I'm grateful I don't have that problem.