Within five days, anterior cruciate ligament injuries rocked two major sports and completely changed their landscapes for the rest of the season. The circumstances surrounding these events will likely be questioned for years to come.

Last Saturday, while still playing late in a playoff game despite his team well ahead, 2011 NBA MVP Derrick Rose performed one of his well-known jump stops. Only this time, unlike the tens of thousands of times before, Rose’s knee buckled. Every Chicago Bulls fan in the United Center and NBA fans everywhere held their breath. Their worst fears were quickly confirmed. ACL.

Thursday, New York Yankees relief pitcher Mariano Rivera was chasing fly balls in the outfield before his team’s game against the Kansas City Royals. Approaching the center field wall, his knee buckled. Teammate and future Hall of Fame third baseman Alex Rodriguez witnessed Rivera’s knee crumbling and reacted as most Yankees fans and baseball fans would, exclaiming, “Oh, my God. Oh, my God.” An MRI soon confirmed what Rodriguez likely feared. ACL.

As a sports fan, news of the injuries of Rose and Rivera should shock me, but I think we’re growing accustomed to those three letters. We hear ACL tears mentioned in every sport these days. But it’s not supposed to happen to the best player in the NBA, right? Or to the best closer in the history of baseball?

Unfortunately ACL tears seem to be an equal opportunity injury. All athletes who play sports that require jumping and cutting, or ones that involve physical contact, are at risk — male or female, young or old, elite or recreational. As many as 175,000 athletes and active people tear this ligament and undergo surgical reconstruction in the United States every year.

The anterior cruciate ligament is the main stabilizing ligament inside the knee. It doesn’t wear out over time. Instead, it tears with specific traumatic events. One of two classic mechanisms typically occurs. The athlete might land from a jump on his foot with the knee extended and the knee buckles, as Rose seemed to do. Or he runs and twists the knee with the foot planted, similar to what Rivera did. The athlete feels a pop as the ligament tears, and he goes down. In a few seconds, he’s out for the season.

For fans critical of Chicago Bulls coach Tom Thibodeau for leaving Rose in for the final minutes of a game that was already decided, or fans critical of Yankees manager Joe Girardi for allowing Rivera to chase fly balls, I would urge caution.

Arguing that these injuries would not have occurred had the players not been in these situations is misleading. Rose has been using that jump stop his whole career. He is known for it. His ACL could have given out in a jump stop earlier in that game, in February, in high school or college.

Rivera is well known for chasing fly balls before games. He has done it his entire career. MLB columnist Buster Olney suggested recently that scouts have noted that Rivera could be one of the best center fielders in baseball if he wasn’t a pitcher. Right or wrong, he caught fly balls before the game Thursday, and he went down. But Rivera could have torn his ACL chasing a ground ball and turning to throw to first base just as easily.

Now sports fans across the country will wait to see how these superstars recover. When will Derrick Rose return next season, and will he regain his MVP form and explosive jump stop? Will Mariano Rivera ever pitch again? What effect will their injuries have on their teams and the champions in their sports? It’s hard to believe that a small ligament can affect so much. But ACL tears can and do happen. To anyone.

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