Sports Medicine Research: In the Lab & In the Field: ACL Risk – It’s In Your Genes (Sports Med Res)
Wednesday, March 19, 2014

ACL Risk – It’s In Your Genes

Genes encoding proteoglycans are associated with the risk of anterior cruciate ligament ruptures

Mannion S, Mtintsilana A, Posthumus M, van der Merwe W, Hobbs H, Collins M, & Septemeber AV.  British Journal of Sports Medicine.  2014 Published Online First: doi: 10.1136/bjsports-2013-093201

Take Home Message: Individuals with a history of an anterior cruciate ligament injury are more likely to have certain genetic variations compared with individuals without a history of a knee injury. While these findings are novel and interesting, researchers need to conduct more research to understand the multifactorial genetic risk behind anterior cruciate ligament injuries.  

If we could identify factors that may predict who is at an increased risk for anterior cruciate ligament (ACL) rupture then we may be able to implement individualized injury prevention programs.  Genetic variants may change ligamentous properties, predispose an individual to an ACL rupture, and thus be an important risk factor for an ACL rupture.  Mannion and colleagues compared the presence of genetic variations between 227 individuals with an ACL rupture history and 234 healthy controls.  All of the participants were physically active and Caucasian. The authors also analyzed a subset of 126 individuals with a history of a noncontact ACL rupture.  They evaluated 10 genetic variants (single nucleotide polymorphisms) among 5 genes that encode proteoglycans, which influence the structural integrity of ligaments. Individuals with a history of ACL injury (34%) were more likely to have a genetic variation in a gene encoding aggrecan, a proteoglycan, compared with healthy controls (28%).  Females with a history of an ACL injury were also more likely to have variations in the gene encoding decorin, another proteoglycan, compared with female healthy controls. 

This is one of the first studies to investigate and identify genetic variations that may be related to a history of an ACL injury.  These findings help us understand that an ACL may be at more risk for injury due to changes in proteoglycans, which may alter the ligament’s tensile threshold.  At this point in time, this does not directly affect clinical treatments; however, these findings could inspire new interventions to address changes in proteoglycans and eventually help us identify individuals “at-risk” for an ACL injury.  This may help us prevent injuries by identifying athletes at risk and offering them individualized injury prevention programs.  While the authors showed that genetics may influence the risk of ACL injuries, it only focused on 10 variations of 5 genes.  Since the risk of an ACL injury is likely influenced by many genes, it may be advantageous to conduct genome-wide studies to encompass all of the possible genes and variations that influence the risk of ACL injury. We have repeatedly seen that genetic variations may influence the risk of injury and that it could influence how we practice but we’ll need to watch this area of research carefully to see how it unfolds.    

Questions for Discussion:  Do you think that genetic testing will change the future of athletic participation (e.g., prevention programs, withheld from certain sports)?  What if you had a patient or family member who tested positive for a genetic variation that made them more susceptible to an injury – would you still permit them to participate in activities that made the risk higher? 
    
Written by: Nicole Cattano
Reviewed by: Jeffrey Driban

Related Posts:
Mannion, S., Mtintsilana, A., Posthumus, M., van der Merwe, W., Hobbs, H., Collins, M., & September, A. (2014). Genes encoding proteoglycans are associated with the risk of anterior cruciate ligament ruptures British Journal of Sports Medicine DOI: 10.1136/bjsports-2013-093201

2 comments:

Liz said...

If someone has a genetic variation increasing their risk of injury I think they should be allowed to continue participation in their sport. There are several other risk factors that can predispose an athlete to an ACL injury but they are still permitted to play. For example, increased Q angle, strength differences between quad and hamstring muscles, playing conditions. There has also been research suggesting that females are at higher risk during there menstrual cycle. As clinicians we are aware of these other risk factors but we don't tell athletes they can't participate because they are menstruating or because their Q angle is too large. We have no way of knowing whether or not they will actually end up with the injury for which they are at risk. Athletes assume a certain amount of risk for injury in whatever sport they choose. Clinicians can help reduce risk by monitoring playing and field conditions, ensuring equipment fits properly, implementing prevention programs. We can inform the athlete of their increased risk caused by their genetics and put in place preventative rehab programs or instruct them to wear a prophylactic brace but I think it should ultimately be up to them to continue playing. If we say that someone can't play a particular sport because they are at increased risk for ligamentous injury then what happens to all the athletes who have had multiple ankle sprains and continue playing sports in which sustaining an ankle sprain is almost inevitable? Do we tell them after x number of ankle sprains they have to find a different sport?

Nicole Cattano said...

Liz-Thank you for your comments. I think you bring up some very interesting points to support this. Genetics is revealing that their role in injury predisposition is a lot higher than I think the field has ever realized.

While I absolutely agree with you about being informed clinicians and that we can educate the athlete's regarding their risk, would their perhaps being a chance that during a vulnerable stage of development that we could modify how or at what level athletes are participating in their sport?

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