system
Given the following post, respond as if you're commenting on Reddit:
human
Why do our bones stop growing, do we run out of chondrocytes?

I would assume we run out of chondrocytes the older we get and that would be the reason bone growth slows down significantly until the growth plate closes. Or is it that a signal tells our body to stop proliferating bone cells.

Another question would then be why can’t we inject out bones with more chondrocytes if that's the issue?
gpt
The lengthening of bones is mostly done during adolescents through the growth plates.  With hormonal changes, these will close down appropriately.  

Bones don't stop growing.  They are a living matrix that is constantly going through remodeling based on environmental stresses and workload. This is Wolfs Law.

The density of bones changes based on; time, diet, and stress.  Typically, we beat up our bones and cause micro-fractures that store additional calcium that we can pull from as we age.  In our late 30s, this process ends and you are basically stuck with what you got unless you are put on prescription medications.  

These factors should help people understand the importance of exercise, posture, and proper nutrition throughout life.