UTK Special 2/3/26

Getting a bit over my skis

This isn’t the normal UTK, but it’s an interesting enough sports medicine story and a big enough one that I felt comfortable that many of you would be interested. I also know I promised you an announcement once I got back, but that’s been delayed, but I promise, you’ll like it and I hope it will be soon.

If you were writing the script for a sports drama and someone pitched you the idea that Lindsey Vonn would seriously consider racing the Olympic downhill with a completely ruptured anterior cruciate ligament, you would pause, ask for a beat, and then ask whether that was really the twist you wanted. Truth is once again stranger and riskier than fiction.

Vonn crashed in a World Cup downhill in Crans-Montana, Switzerland, just a week before the Milan-Cortina Games were to begin. What initial uncertainty on the mountain quickly became clear in scans was a complete rupture of the ACL in her left knee together with bone bruising and some meniscal damage. In most athletes at any level, anywhere, that diagnosis would mark the end of both the season and any realistic chance of competing for months if not longer. A complete ACL rupture (Grade III sprain) is not an injury in the way a bruise or a mild sprain is. It means the ligament that resists forward motion of the shin bone and controls rotational forces is gone. Torn in two, or close. That’s the structural heart of the knee, and without it, a joint is fundamentally unstable.

But Vonn is not a typical athlete and this is not a typical story. She is forty-one, a three-time Olympic medalist, and two seasons into a comeback after a six-year hiatus that included knee replacement surgery* on the opposite side of the recently injured knee. She came back not just to compete but to win and she did exactly that with multiple podiums and victories on the World Cup circuit this season, leading the downhill standings and reminding everyone that even a titanium implant does not diminish her racing prowess.

In Cortina d’Ampezzo, she confirmed what her team and everyone watching already suspected: she feels stable enough to try. She reports no significant swelling and says the knee, with the help of a brace and intense physical therapy over the last few days, feels like it can handle one loaded descent. She skied again after the injury. She stood in front of the press and sounded like an athlete making a calculated choice rather than an emotional one. She knows the risks. She knows what her knee is missing. She also knows that the chance to ski one last Olympic downhill, to chase a medal on the biggest stage of her sport, may not come again.

From a sports medicine perspective, this is a bold gamble. A torn ACL in an elite athlete normally triggers a reconstruction and a six-to-nine-month rehabilitation timeline before any high-stress activity is attempted. In a sport like alpine skiing, where speeds exceed 80 miles per hour and forces twist and torque the knee on every turn, the absence of that ligament presents a significant risk. That risk is not theoretical. It’s what keeps athletic trainers awake at night. The bone bruise and meniscal involvement compound that risk, adding pain potential and the threat of further cartilage injury if the knee is overloaded.

Yet we have precedent in skiing and other sports of athletes functioning at high levels with ACL deficiencies. In the World Cup ranks, racers have competed, and occasionally succeeded, with chronic ligament instability. Breezy Johnson skied and won with no ACL in one knee for extended periods. Other athletes have deferred surgery, have managed instability with strength and proprioception, and have found ways to keep skiing where other athletes might have faded. Those stories are not homogenous and they are not complete analogues, but they are reminders that elite neuromuscular control and sport-specific strength can compensate far more than casual observers might expect.

That compensation is key. A brace can provide external constraints, limit some motions the ACL would normally control, and offer a sense of containment. But it does not replicate the ligament’s function. On a knee like Vonn’s, the muscles, particularly quadriceps and hamstrings, become the first line of defense against instability. Hers are formidable. For most skiers, that wouldn’t be enough. For someone whose lower-body strength has been honed to world-class levels, whose proprioceptive awareness rivals that of any athlete in any sport, and whose technical precision minimizes unnecessary stress on the joint, the muscles and nervous system can do extraordinary work to maintain control. Even so, it remains a compromised system and not a healed one.

The narrative here is about more than biomechanics. It is about timing and legacy. Vonn is attempting to compete in her fifth Olympics, an extraordinary achievement in itself. The downhill race she is targeting begins training runs later this week and culminates in the medal event on Sunday. If she starts, she wants to do more than finish - she wants to compete. She has been clear that she knows her chances are diminished compared to a week ago, but she also believes there is a chance worth taking. In her own words, “as long as there’s a chance, I will try.”

For a medical community watching this, the tension is palpable. There is admiration for what she has done and caution about what she is attempting. An ACL sprain is not something that “feels better” quickly; it’s something that is structurally altered. A brace and strong muscles can provide support, but they are not a substitute for healed tissue. Every turn down a track like Tofane, with its high speeds and constant redirections, invites loads that test the limits of anterior and rotational control. There is no guarantee that the knee will hold and there is a real possibility that further injury could occur.

Yet Vonn has never been an athlete to bow gracefully to limitations. A scan of her career shows repeated recoveries from severe injuries, repeated returns to top form, and repeated defiance of expectations. She has fractured bones, suffered ligament tears, and come back from them; she has navigated surgeries and setbacks that would have ended lesser careers. Now she is trying something that would have seemed impossible even a decade ago, competing at the highest level in the most demanding discipline of her sport with a knee that, by traditional standards, should be off limits.

Whether this gambit ends in triumph, in a respectable finish, or in an early exit, it is already a statement about the evolving intersection of elite performance and risk management. Medicine can assess tissue integrity and mechanical support, but it cannot quantify the athlete’s will. Vonn’s choice is not about denial of injury; it’s about a calculated wager on control, strength, experience, and timing. She knows the numbers; she knows the stakes. She also knows that at this point in her career, opportunity may matter more than certainty.

When she stands at the top gate in Cortina, she won’t just be skiing down a mountain. She’ll be skiing down the story of her own resilience, one last time on the sport’s biggest stage.

*Vonn didn’t get a traditional total knee replacement like the surgery most older adults receive for end-stage arthritis. Rather, she underwent a robot-assisted partial knee replacement (unicompartmental arthroplasty) in her right knee, where only the most damaged portion of the joint was resurfaced with titanium and polyethylene components. This preserves healthy bone, ligaments, and soft tissue around the rest of the knee and results in a much more natural-feeling joint with faster recovery and better proprioception — crucial for high-demand movement in elite athletes.

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Let’s get a bit further in the weeds of the technical and biomechanical issues:

When you talk about knee biomechanics in the context of a completely ruptured anterior cruciate ligament (ACL), you are talking about fundamental stabilization mechanics that the human knee depends on, especially in high-loading, high-speed sports like downhill skiing. The ACL is one of the primary internal restraints of the knee. It runs deep inside the joint from the femur to the tibia and resists anterior translation of the tibia (forward slippage relative to the thigh bone) and helps control internal rotation of the shin relative to the thigh. At normal speeds or slow motion, muscles can often make up for some passive laxity by stiffening quickly, but at high speeds and forces, like during an elite downhill run, that ligament has a unique structural role that muscles and bracing can only partially compensate for.

Knee biomechanics are an interplay between passive stabilizers (ligaments, joint capsules) and active stabilizers (muscles). In an intact knee, the ACL contributes up to 85 percent of the restraint to forward tibial translation at functional flexion angles; that’s how important it is in resisting knee collapse under load. Once that ligament is absent, muscle forces and neuromuscular control become the dominant stabilizers. The quadriceps works to control knee extension and shock absorption, while the hamstrings counteract forward shear and resist tibial translation. The gastrocnemius and other calf musculature also contribute dynamic control in weight-bearing tasks. Strength in these muscle groups matters enormously, because the knee relies on them to resist the very motions the ACL would normally control.

From a risk perspective, skiing without an ACL, especially immediately after a complete rupture, is inherently dangerous. Extreme twisting, torsion, and landing forces can provoke secondary injury, such as meniscal tears or cartilage damage, because the knee’s passive restraint is gone. High-demand activities like rapid directional changes and uneven terrain loading increase the chance that compensatory muscle forces are not enough to prevent abnormal motion. Studies consistently remind clinicians that ACL-deficient knees are unstable under high loading unless supplemented by external support and excellent neuromuscular control.

Which brings us to bracing. Functional knee braces aim to mechanically limit abnormal motion and potentially reduce anterior translation and excessive rotation around the joint. Biomechanical studies have shown that certain rigid and functional braces can reduce peak frontal plane motion and rotational excursion compared to an unbraced ACL-deficient condition, at least in controlled settings. Moreover, earlier cohort research in skiers suggested that those wearing functional braces after ACL reconstruction had lower rates of subsequent knee injury than similar skiers who did not brace. That doesn’t mean bracing replicates the native ACL - no commercially available brace perfectly reproduces the internal ligament’s force-flexion profile - but it does help reduce gross instability and offers some mechanical resistance under load.

Look for this on race day or in training runs:

•Vonn’s knee brace will not be a soft sleeve alone. It’s almost certainly a highly custom rigid or semi-rigid functional brace designed to resist rotation and anterior translation.

•If she appears cautious through transitions and turns that require abrupt deceleration or change of direction, that reflects the reality that muscles are the primary stabilizers in an ACL-absent knee.

•Watch whether she presses aggressively into compressions or targets straight gliding lines. Dynamic knee positions that challenge rotation and shear are where instability and risk are highest.

Finally, even the best braces work with the neuromuscular system rather than replacing it. That’s why quad and hamstring strength, timing of muscle activation, and proprioceptive control are as crucial — possibly more crucial — than the brace itself. In ACL-deficient knees attempting high performance activity, the brace supplements the musculoskeletal system but doesn’t supplant the need for exceptional muscular control under high forces. In other words, Vonn being exceptional gives her the chance to just have a chance.