Bone is living tissue that is torn down and rebuilt constantly throughout your entire life.

What it means

One population of cells dissolves old bone and another lays down new material, and the skeleton is largely replaced over the course of about a decade. The process is responsive: bone thickens along the lines of stress it experiences, which is why the racket arm of a tennis player carries denser bone, and why astronauts lose it in the absence of weight.

The claim comes from NIAMS, and the page it comes from was read on 2026-08-27 to confirm it still says this.

This is not the kind of claim that goes out of date, which is why it was set as a puzzle rather than a fact with a shelf life.

Solve it yourself

This fact is a cryptogram here: 76 letters over 19 different ones, graded hard.

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Nearby in the collection

The facts either side of this one.

• NCBI Bookshelfeasy, 71 letters
• PLOS Biologymedium, 75 letters
• NCBI Bookshelfmedium, 77 letters
• MedlinePlusmedium, 69 letters

About as hard as this one

Scored closest to it by the model behind our guide to solving cryptograms.

• National Human Genome Research Institutehard, 67 letters
• NIDDKhard, 74 letters
• NIDCDhard, 74 letters
• Royal Society of Chemistryhard, 70 letters