Valtola et al and Honkanen et al (PMID: 11792591, 9692074) found that primary risk factors for ankle fracture are cigarette smoking and a high body mass index. According to Seeley et al (PMID: 8864910), although low bone density is a risk factor for other fractures, it has not yet been shown to be a major risk factor for ankle fractures.
An avulsion fracture of the ankle (a small fleck of bone seen on radiographs just distal to a malleolus) is an ankle sprain equivalent. The primary injury is to the ligament, not the bone. The fleck seen is a fragment tugged off the bone when the calcaneofibular ligament was pulled, much like a Just as a piece of masking tape yanked briskly from a wall may take with it a sliver of paint as well. (That piece of paint, one might say, has been “avulsed” from the wall.) An avulsion fracture is not a structurally significant bone injury but its presence , a sprained ligament may yank with it a small sliver of bone: a so-called avulsion fracture. The finding is important only that it informs the viewer that an ankle sprain is present.Image Removeda sprain has occurred; the bony injury is itself insignificant.