Everyone has at least some “postural sway,” the term for body movement that occurs horizontally—either left-right, called mediolateral sway, or forward-back, called anteroposterior sway— when standing in one place. It’s measured by standing on a force plate that records changes in the center of pressure along two perpendicular axes while you look at a fixed point.
Postural sway is an important component of balance (minimal sway indicates better balance), and it tends to worsen with age. Other factors that can increase postural sway include scoliosis and kyphosis (two types of abnormal spinal curvature), weak muscles, and neurological changes due to such conditions as a stroke, middle ear infection, peripheral neuropathy, or dementia.
A fracture factor
Several studies have linked higher postural sway with a greater risk of falls, which are a leading cause of fractures. Now some research is finding that postural sway itself may be an independent risk factor for fractures. In a paper published in the Journal of Bone and Mineral Research in 2019, for instance, researchers analyzed data from 1,568 postmenopausal women in Finland (average age 59) who participated in a long-term study of bone health. The women’s postural sway (mediolateral, anteroposterior, and total) was measured at the start of the study.
Over a follow-up of around 11 years, those who scored in the highest quartile of postural sway—particularly mediolateral sway—had double the likelihood of fracturing a bone compared to women in the lowest quartile. The association held up after the researchers adjusted for age, height, alcohol intake, previous fractures, smoking, and leg strength.
While more research is needed, the authors noted that adding postural sway to fracture risk assessment tools—like the well-known FRAX calculator—“might improve their predictive capability.”
Some earlier studies have also found an independent link between postural sway and fractures. In a 2011 Japanese study of more than 700 older women, those with the highest postural sway velocity—meaning the rate at which their center of gravity moved while they were standing still—were more than twice as likely to have a vertebral or limb fracture over six years as those with the lowest postural sway velocity.
And in a small study in Clinical Interventions in Aging in 2016, in which researchers compared 20 older adults who had experienced a “frailty fracture” (a fracture likely due to osteoporosis) with 21 fracture-free older adults, the fracture group had more side-to-side sway in their lower back and pelvic area when walking.
Minimizing the movement
It would be unrealistic to screen large portions of the population for postural sway, so many of us may never know if we have it or to what extent. But it makes sense to do what you can to reduce it. Some factors that cause postural sway aren’t modifiable (age or a stroke, for example), but others may be. Chronic ankle instability may increase swaying, as can fatigue in the muscles of the torso, hips, knees, and ankles. Strengthening these muscles might help mitigate the sway, plus help protect bones in other ways. It’s also a good idea to do exercises to improve your balance; for ideas, see tinyurl.com/ACEbalance.