A recent study found that human foot bones undergo specific shape changes with increasing size, which may help mitigate joint contact stress and preserve foot function across a range of body sizes.

In the study, published in Royal Society Open Science, researchers from the University of Queensland and Queen's University used computed tomography (CT) scans of the talus and calcaneus from 36 healthy adults to assess whether these bones scale isometrically or allometrically.

“If human skeletal shape increases proportionally with size (isometric scaling), we would expect exponential increases in joint contact stress as individuals become larger,” the study authors wrote. “However, if skeletal shape changes as a function of size (allometric scaling), this can mitigate increases in joint contact stress by changing the surface area (SA)-to-volume ratio,” they added.

The researchers found that the talus scaled isometrically, showing no significant shape changes related to size. In contrast, the calcaneus scaled with negative allometry, meaning its surface area increased at a slower rate than expected under isometric scaling conditions. As the calcaneus increased in size, it became relatively taller (superiorinferiorly), wider (mediolaterally), and shorter (anteroposteriorly), producing a more cube-like appearance.

The researchers suggested that these shape adaptations may play a role in mitigating internal bone stress as skeletal size increases. Although the calcaneus overall showed negative allometry, its articular surfaces scaled isometrically, indicating that these surfaces were growing at a relatively faster rate compared with the surrounding bone.

At the level of the subtalar joint complex, shape-size relationships were also observed. These joint-level adaptations appeared to be driven primarily by changes in the calcaneus.

“These findings have important implications for the development and progression of degenerative joint conditions such as osteoarthritis,” the study authors indicated. “Further research exploring how joint posture and mobility interact with shape and size to determine joint contact mechanics have the potential to enhance the management of these conditions via surgical and conservative means,” they concluded.

The authors declared no competing interests.