[HappMacDonald]

Is that causative though? Or do people with great cartilage simply enjoy running more because it isn't as painful?

[TeaBrain]

Why this way of looking at cartilage is a misconception is explained in the study cited by the top level comment. Cartilage in different parts of the body has been shown to be different ages, indicating that it rejuvenates and that there there isn't just a single set of good or bad cartilage.

[schwartzworld]

Any exercise is going to be uncomfortable if you haven’t conditioned yourself.