We as a society love sports. Football, basketball, and baseball are huge parts of our culture here in the United States. But even abroad, sports are popular as well. Soccer is incredibly popular overseas. What do these sports have in common? Running. According to this article from John Hopkins Medicine, basketball, baseball and softball, bicycling, football, and soccer have the most injuries in children aged 5-14. The injuries children may receive in activities like ice hockey, in-line and roller skating, skateboarding, sledding and toboggan, snow skiing and snowboarding, and trampolines all pale in comparison to sports that require running, with bicycling being the only outlier (John Hopkins Medicine).

Now just because there is a correlation between sports that require more running and the amount injuries that occur from these sports does not mean there is a direct correlation between the two. There could easily be a confounding, or third variable that effects this relationship, the obvious ones being the size of the players, or the physicality of the sport. This study also does not say what kind of injuries these children are suffering from. So rather than focusing on that study, which deals with children, it would be easier to look at this article, which deals with professional athletes.

According to Tarek O. Souryal, an M.D. who has worked for the Dallas Mavericks, a professional basketball team in the NBA, the ACL helps with making quick cuts which is commonplace in sports such as basketball, football, and even soccer. ACL injuries according to this article are pretty much exclusive to athletes, happening over 250,000 times a year to them.

With athletes receiving ACL injuries at that clip compared to ordinary people, the prospect of chance being the reason for the correlation between people tearing their ACL who play sports involving running and people who don’t is highly unlikely. However, maybe there is a third variable that impacts why these athletes tearing the ACL? Maybe athletes’ bodies have something, perhaps bone structure, that causes more injuries? Luckily this article also takes a look at that!

Souryal noticed a confounding variable which found that some people in the world have different bone structures and these structures do indeed make them more prone to these ACL injuries. Souryal said that if the area where your ACL and PCL are located is small, the ACL has less room to make these cutting movements, you are more likely to tear you ACL. As a matter of fact, you are 26 times more likely to do so.

Additionally the article states that in 1992, Souryal took the knee X-Rays of 1,000 different high school athletes. The athletes who were selected were monitored for two years. By looking at their notch, they found that the ones with a narrow notch were the ones tearing their ACL. The article said the results were so overwhelming that Souryal no longer continued the study. This study helps to show that bone structure is indeed the third variable between athletes tearing their ACL, however there must be more studies done. 1,000 people is a lot of people to study, however, even more can be used in the study. If I was the person doing the experiment, I would separate athletes with narrow regions where their ACL and PCL are located to those with wide regions and see who tears there ACL more. Because this is an observational study, this evidence is not concrete as much as an experimental would be. The reason it can’t be experimental is because it would be unethical to make it so people would tear their ACL. This would help prove or disprove the notion that bone structure is indeed a third variable, although it would not be as effective as an experimental study. 

Are we are not supposed to be playing sports that require such cutting movements with our legs? Maybe our society has glorified activities that we were not born to play. There is certainly evidence that supports the correlation between the number of ACL tears and those who are athletes. However, maybe it is because of these athlete’s bone structure and not because they are athletes. More research and better technology will certainly help us find this out. Judging from the research, I would say that humans are not supposed to play sports, especially those with bone structures that make them prone to ACL injuries. The cutting required to play soccer, basketball, and football at a high level is just too hard for the human body to handle.