Hmm, I think you should be kind to your knees, young sir. You'll miss them when they're gone.

A lot.

My friend was taking a dance class and he thought, hey, Jazz dance should be light and good exercise.

Then he realized it was brutal and good exercise. Then he started having problems with his knee joints but decided, eh, I'll just tough it out even though I'm taking a dance class too advanced for my body's ability to perform safely.

Now he has to have physical therapy for his knees and they may never work prop'ly like again.