"While we put in metal screws and rods to ensure that the bone heals straight, the actual healing of the bone remains a biological process," O'Keefe says. "And fractures that happen during different times in life have different abilities to heal."
Critical to the bone healing process will be a thin sheath of cells, known as the periosteum, which enshrouds all of the bones in the body. The periosteum contains stem cells which will eventually form the cartilage and bone tissue required to fill the break.
The older you are, the more slowly these stem cells work to repair injury.
"The cells that line your bones as you get older have less of an ability to drive healing," O'Keefe says. "Comparing the governor as an adult to when he was an adolescent, his ability to heal now is slightly slower than it was."
Fortunately for Schwarzenegger, the femur is one of the bones that has a high number of these stem cells. And researchers are currently looking at ways to take advantage of these cells to help patients heal more quickly.
"As we continue to study these stem cells, we will be able to understand why stem cells that are older don't behave in the same way as those that are younger," O'Keefe says.
"Once we understand that process, we can manipulate the stem cells and supply signals that potentially enhance repair."
With continued medical developments, many researchers hope that typical bone breaks experienced by seniors will shift from those attributable to osteoporosis and other forms of bone deterioration to those from episodes like Schwarzenegger's.
"We have previously seen aging associated with arthritis, poor fracture repair. This has been seen as an inevitable part of getting older," O'Keefe says. "As the baby boomer generation ages, what we hope to do is manipulate those types of processes thought of as inevitable in order to correct these processes so people can be more active."
And even before new treatments hit the scene, Messmer says middle-aged Americans may do well to follow Schwarzenegger's example and engage in exciting physical activities -- provided they do so safely, of course.
"Someone who is fit should not limit himself or herself due to age, for the most part," Messmer says. "Balance begins to be affected in the 70s, so something like rock climbing might not be advised. But skiing, tennis, etc., should not be limited just due to age."