For action sports stars accustomed to leaving fans breathless with acrobatic aerial stunts, those same athletes are now in shock themselves.

Canadian freestyle skier Sarah Burke remains in critical condition at the University of Utah Hospital in Salt Lake City after a seemingly unremarkable fall last week. Burke, a six-time Winter X Games medalist and winner of the Women's Ski Superpipe in 2011, was training in Park City and preparing to defend her title at Winter X Games Aspen later this month.

She landed a jump toward the end of a training run but fell and hit her head. Peter Judge, head of the Canadian Freestyle Ski Association, emphasized that Burke was not trying unusually difficult tricks. "It was nothing out of the norm, nothing on the extreme end of the spectrum." However, within minutes, she was airlifted to Salt Lake City.

Burke underwent surgery to repair a tear in her vertebral artery. "With injuries of this type, we need to observe the course of her brain function before making definitive pronouncements about Sarah's prognosis for recovery," said Dr. William T. Couldwell, the chair of neurosurgery at the University of Utah.

Dr. Safdar Ansari, the neuro- intensivist coordinating Burke's care, addressed her situation later in the week. "With traumatic brain injury, our care is focused on addressing the primary injury and preventing secondary brain damage, as well as managing other injuries sustained at the time of the accident, all of which requires close monitoring and intensive care. At this moment, Sarah needs more time before any prognosis can be determined."

I discussed Burke's injury with Dr. Raymond Turner, co-director of the MUSC Stroke and Cerebrovascular Center. He explained that the vertebral arteries are at risk for injury from whiplash-type injuries because they run inside the bones of the cervical spine and are therefore tethered in relation to the head. "Interruptions in the blood flow in these vessels can result in brain injury that may be minimal, such as short-term coordination problems or dizziness, to something that is life threatening," Dr. Turner said.

As for Burke's surgery, he described how these dissections can be surgical emergencies. "Ms. Burke has been reported to have a tear in the vertebral artery, also called a dissection. The symptoms of a bleeding vessel in the head can cause severe headaches, confusion, weakness, and if severe enough, coma and death. Repair of this tear should be done urgently to prevent further bleeding. This type of injury can be fatal in some cases, however, fortunately that is not always the case, and many patients can recover in weeks to months."

So as we wait to see if Burke recovers, we can wonder why these injuries happen. But honestly, we know the answer to that question. This is the nature of these action sports. The halfpipes are getting bigger. The stunts are becoming riskier, with more height and flips. And yet, it is the athletes themselves pushing to perform more dangerous stunts.

Even if I wanted to do so, there would be no sense for me to argue that the sports' governing bodies should regulate them more closely. These athletes know exactly what they are getting into. Snowboarding star Gretchen Bleiler wrote in espnW.com: "As pro snowboarders, skiers, etc., we all know that what we do is risky. But when accidents produce results like this we're left praying and asking ourselves questions. Is it worth it? Why did this happen? What are we doing?"

Ironically, the Superpipe in Park City is the same one where snowboarder Kevin Pearce suffered a traumatic brain injury two years ago. And Burke herself is no stranger to injury, having missed a large part of the 2009 season after fracturing a bone in her lower back.

Now the freestyle skiing and snowboarding community is rallying around one of its pioneers. Burke has been admired for her poise, confidence and strength. The former ESPY winner for Best Female Action Sports Athlete will now need every bit of those qualities to recover.

Sarah Burke's success shows not only in the medals she has won in halfpipe skiing but also in getting the sport itself accepted. She lobbied for its inclusion in the Olympics, and in 2014, the sport will make its debut in Sochi, Russia. Burke, long thought to be the favorite for the sport's first Olympic gold medal, might now just be lucky to watch it as a spectator.

Dr. Geier is Director of MUSC Sports Medicine and an orthopaedic surgeon. For more information about skiing injuries and other sports medicine topics, go to drdavidgeier.com.