Researchers at the University of California - Davis have shown that elderly women who had an upper body fracture or multiple fractures had more loss of hip density compared to those who who did not fracture. Systemic bone loss may increase the risk of future fractures. 

The Study of Osteoporotic Fractures included nearly 4000 elderly patients who were followed with hip BMD measurements at year 6 and year 10.  A subset of women (n = 3783) was analyzed for annual total hip BMD change between study visits 4 and 5 and between study visits 5 and 6 to evaluate change in total hip BMD during these 2-year intervals.

Women with incident fracture exhibited reductions in total hip BMD of 0.89 and 0.77% per year, while women who did not have a fracture exhibited reductions had less total hip BMD loss (0.66% per year)  

Thus there may be systemic bone loss response initiated by fracture that is independent of activity limitations.  Further study is needed to understand these mechanisms so as to reduce future fracture risk.