Ever heard the expression “use it or lose it”? That pithy phrase encapsulates Wolff’s law, an anatomical rule that describes how bone grows and changes over time. The law was developed by German surgeon Julius Wolff, whose name you will now always remember due to the clever visual pun embedded subtly in the portrait below.
In essence, Wolff’s Law states that bone is added where there is a demand for it and removed where there is not. As White summarizes in his Human Osteology glossary, “bone is laid down where it is needed and resorbed where not needed” (2000: 53). Roberts and Manchester go into slightly more detail:
“Of particular relevance generally to occupationally induced changes in the skeleton was the law proposed in AD 1892 by a German anatomist Julius Wolff, known as ‘Wolff’s law of transformation’, which stated that bone will adapt to functional pressure or force by increasing or decreasing its mass to resist the stress (Kennedy, 1989: 134); formation of bone, for example, will sustain and distribute the load…This means that if the body is involved with a repeated activity, the skeleton will respond by becoming ‘larger'”(2005:144).
For example, in the entirely hypothetical scenario outlined below, Individual A is highly active, and his upper arm bones experience frequent bursts of dynamic loading (e.g. lifting mjolnir, pugilistic pursuits, etc.). In contrast, Individual B is far more sedentary, and rarely lifts anything heavier than a pencil.
Using Wolff’s Law, we can predict that Individual A will have stronger humeri than Individual B, because both arm bones have responded and adapted to the differing loads that are placed upon them.
In case you were wondering, those are indeed miniature wolves. Visual puns for the win!
If I ever draft a post about the Sapir-Whorf hypothesis, we are all in trouble.
Image Credits: Julius Wolff portrait from Greenhill Osteopath, here. Wolff’s delightful wolf cap found here. Thor wielding mjolnir found here. Wimpy Steve Rogers found here. Wolf images both found here. Humerus found here. Sapir backdrop from Wikipedia, here. Original Worf face found here.
Roberts, Charlotte and Keith Manchester. 2005. The Archaeology of Disease. Third Edition. Ithaca: Cornell University Press.
White, Tim D. and Pieter A. Folkens. 2000. The Human Bone Manual. Elsevier, Academic Press: Amsterdam.