A law stating that bone density changes in response to changes in the functional forces on the bone. Wolff (1836–1902) proposed that changes in the form and function of bones, or changes in function alone, are followed by changes in the internal structure and shape of the bone in accordance with mathematical laws. Thus, in mature bone where the general form is established, the bone elements place or displace themselves, and decrease or increase their mass, in response to the mechanical demands imposed on them. The theory is supported by the observation that bones atrophy when they are not mechanically stressed and hypertrophy when they are stressed. Although Wolff's proposal relates specifically to bone, the law has also been applied to other connective tissues such as ligaments and tendons. See also bone remodelling, stress continuum.