How is Lindsey Vonn skiing on a torn ACL? Why downhill is different than other sports

It’s the biggest question in the first days of the Milan Cortina Olympics: How is Lindsey Vonn possibly skiing on a knee with a ruptured anterior cruciate ligament?

It’s the sort of injury that generally sidelines top athletes for about a year. Vonn was back on the snow within days.

On Saturday, she completed her second training run at the Games. She is scheduled to race Sunday in the Olympic women’s downhill. After her first training run Friday, her coach, Aksel Lund Svindal — like Vonn, an Olympic gold medalist in the downhill — said she can still medal, and even win the gold.

Saturday brought a slight knee buckle after one jump when her left arm flew up to maintain balance, but nothing that seemed like it would prevent her from getting into the starting gate Sunday.

What the what?

Let’s be clear — this is an outrageous endeavor. There are not many skiers who could pull this off or would even want to try. Other top skiers have competed for years with ACL tears, the main ligament that connects the thigh bone to the shin bone and provides stability to the knee. This is far from normal.

That said, experts in sports medicine say they are not as shocked as everyone else. It’s doable for a variety of reasons having to do with Vonn herself, the nature of skiing the speed events of downhill and super-G, and basic biology and modern medical treatment and equipment, including a state-of-the-art brace.

“We used to have a saying, ‘Don’t operate on the X-ray, operate on the patient,'” said Bill Mallon, a fellow of the American Academy of Orthopaedic Surgeons and an expert in Olympic sports. “We should probably say the MRI now, but it applies in this case.”

Perhaps the most important feature of Vonn’s injury so far is that she hasn’t experienced enough swelling to render her unable to ski, and she and her medical team have been able to control the swelling present. No one knows exactly why her left knee hasn’t swelled up like a balloon, which often happens with an ACL tear.

Dr. Jordan Metzl, a sports medicine physician at the Hospital for Special Surgery, who has not treated Vonn, said it’s possible this was not the first time she has torn that ACL, since the worst bleeding and swelling occur after an initial tear. Subsequent tears often bleed and swell far less.

The swelling could cause big problems. “The knee would essentially be floating in a jar of liquid and would be far less stable,” Mallon said.

Also, he pointed out that she has other knee ligaments that, for now, are compensating for the tear in the ACL. That could cause some issues over time, but for now, they appear to be doing their job.

Dr. Robby Sikka, a sports medicine expert who has served as the team doctor for the New York Yankees and is the medical director for the Professional Tennis Players Association, said racing speed events offer several opportunities for compensation for an ACL injury. While the ACL prevents the tibia (shin bone) from sliding forward relative to the femur (thigh bone) and provides stability, there are other ways Vonn can stabilize the joint.

The ski boot helps, limiting ankle movement, which reduces stress on the knee, and the binding that attaches the boot to the ski helps maintain the joint’s alignment. Vonn also has incredibly well-developed quadriceps muscles that help hold the knee in place, as well as strong hamstrings and glutes. And, at 41, no one on the mountain has more experience with body awareness.

Vonn’s body awareness was in full flight Saturday in training, quite literally. After the run, Svindal said that bobble after the jump occurred because Vonn has been tending to land on one ski — her right one, which is attached to her non-injured knee, to take pressure off the injured knee. Svindal said that is a fine maneuver if the ski is flat, but if it’s tilted and on a edge, “it’s going to wobble.”

“The impacts here in the landings are flat,” Svindal explained. “It’s a hard impact, and then you should try to land on both feet. It would be safer. But I guess that’s a reflex.”

In addition, she is mostly performing predictable movements. She doesn’t have to make quick, surprising cuts and plant her foot the way a basketball, soccer or football player would. She leans forward and heads down the mountain, which naturally engages the muscles that can compensate for her ruptured ACL. Her events are all about flow rather than the quick cuts of slalom, which would be nearly impossible without a functioning ACL.

Karen Sutton, an orthopedic surgeon with the Hospital for Special Surgery who has worked with the U.S. ski team, said all downhill skiers have something like superhuman strength, given their ability to maintain speeds of 75 mph-95 mph as they fly down slopes with gradients potentially of 65 percent.

Alpine skiing, however, is what physicians refer to as a “Level II pivoting sport, meaning it has less quick, sharp pivoting than Level I pivoting sports like soccer or basketball,” Sutton wrote in a text message.

“When an ACL is not functioning, an athlete recruits all of these muscles to try to counterbalance instability of the knee. The muscles have to be strong and powerful enough to combat extremes of G-forces down the mountain,” Sutton wrote.

“A skier with lightning reaction time, massive muscle recruitment, experience in the sport and the help of a functional ACL brace would be best equipped to attempt a downhill course without an ACL.”

Sounds a lot like Vonn, doesn’t it?

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