Wolff's law

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Wolff's law is a theory developed by the German Anatomist/Surgeon Julius Wolff (1836–1902) in the 19th century that states that bone in a healthy person or animal will adapt to the loads it is placed under. If loading on a particular bone increases, the bone will remodel itself over time to become stronger to resist that sort of loading. The internal architecture of the trabeculae undergoes adaptive changes, followed by secondary changes to the external cortical portion of the bone,^[1] perhaps becoming thicker as a result. The converse is true as well: if the loading on a bone decreases, the bone will become weaker due to turnover, it is less metabolically costly to maintain and there is no stimulus for continued remodeling that is required to maintain bone mass.^[2]

Associated laws

• In relation to soft tissue, Davis's Law explains how soft tissue remolds itself according to imposed demands.
• Refinement of Wolff's Law: Utah-Paradigm of Bone physiology (Mechanostat Theorem) by Harold Frost.

Examples

Tennis players often use one arm more than the other

• The racquet-holding arm bones of tennis players become much stronger than those of the other arm. Their bodies have strengthened the bones in their racquet-holding arm since it is routinely placed under higher than normal stresses.
• Surfers who knee-paddle frequently will develop bone bumps, aka exostoses, on the tibial eminence and the dorsal part of the navicular tarsal bone from the pressure of the surfboard's surface. These are often called "surf knots."
• Astronauts who spend a long time in space will often return to Earth with weaker bones, since gravity hasn't been exerting a load on their bones. Their bodies have reabsorbed much of the mineral that was previously in their bones.
• Weightlifters often display increases in bone density in response to their training.
• Martial artists who punch or kick objects with increasing intensity (or of increasing hardness) to develop striking power to damage opponents, often display increases in bone density in the striking area.

Karate is a martial art that emphasizes striking movements

See also

• Julius Wolff
• Functional matrix hypothesis

References