Everything You Need to Know About ACL Tears
You no longer have to be an avid sports fan to hear about the ACL any more. If you are a parent of a young athlete, a recreational athlete, or weekend warrior, I would surely bet that you have heard of this ligament and its injury epidemic. In our practice, ACL injuries are becoming more common than ever before, with age ranges from children of 12 years old to active adults of all ages. But why? Why are ACL tears in athletes becoming more and more common?
We will get there, I promise.
But first… a little background. What is the ACL?
The ACL is one of the four main ligaments of the knee, along with the Medial (inside) Collateral Ligament, Lateral (outside) Collateral Ligament, and Posterior Cruciate Ligament that connects and stabilizes the femur (thigh bone) to the tibia (big lower leg bone) and fibula (small lower leg bone). As a general rule, ligaments prevent or restrict motion to specific joints. The motions they restrict are determined from their origin and insertion.
- Collateral Ligament
- Collateral ligaments are outside ligaments, as seen below. These ligaments prevent valgus and varus (side to side) stresses to knee
- Cruciate Ligament
- Cruciate ligaments are found deep in the knee joint. The Anterior (front) cruciate ligament and Posterior (back) Cruciate Ligament cross in an ‘X” pattern to prevent front to back sheer stresses on knee joint.
The ACL, specifically, prevents anterior (or forward) translation, and internal rotation of the tibia on the femur. In other words, the ACL also prevents lateral rotation of the femur on the tibia.
How does the ACL play a role in my daily life?
Accelerating, decelerating, reacting, turning, twisting, and jumping, occur in almost every sport, and with these motions, our ligaments, along with muscles, prevent our joints from moving in unwanted or injury susceptible directions. However, when our muscles are broken down, our bodies are fatigued or malnourished, and our minds are not focused on the demanding task at hand, we put ourselves at risk for injury. Now, these are not the only reasons why ACL tears occur, but the fact is that an estimated 70% of ACL tears are sustained through non-contact mechanisms; the remaining 30% result from direct contact. This means, that 70% of the time, we cannot blame the contact sport, or another person for causing us injury.
So here are some facts:
- The majority of ACL injuries (70%) occur while playing agility sports, most often reported in basketball, soccer, skiing and football.
- ACL tears are most prevalent in patients 15-45 years old.
- Female-male ACL tear ratio has been reported to be as high as 9:1 by NCAA statistics.
To explain the reason for females being nine times more likely to sustain an ACL injury than males, please see Figure 1. But, what else goes into that 70% non-contact number?
As touched on earlier, mental and physical fatigue can play an overwhelming role in injury. The concept of “overuse” is an educational piece for not only athletes, but many parents as well. Parents, think back to when you were growing up… what sports did you play, what seasons did they occur in, how many of your teammates had ACL injuries? Many of the athletes whom I encounter in my practices who have had or are currently rehabilitating from an ACL tear report that they are a single sport athlete and play that sport all year round, on different teams possibly even at the same time. While not bad to build skill, our bodies need time rest, muscles time to recover, and minds to mentally decompress. Are the young athletes today, achieving this?
The warm up and cool down
The importance of the warm-up and cool-down cannot be overstressed. A warm up, should consist of active or dynamic movements that prepare and simulate game or practice-like situations, yes even contact movements. These movements and activities should aim to increase heart rate, initiate perspiration, and effectively warm up our bodies for the sport specific activities to come. Without a proper warm up, our bodies, muscles and joints are not properly acclimated to weather, external/environmental factors, or stretch/stress to come. A cool down should consist of static stretching and or foam rolling along with proper nutrient replenishing to allow our muscles, and minds to re-acclimate to normal.
Finally, does field turf increase risk for injury?
The quick answer is that the jury is still out. While multiple research studies have been conducted, researchers have not found substantial evidence for or against field turf. Natural grass can yield many different surface types depending on the weather, while turf does not “give” as much as soil. My recommendations? When playing on turf, use a low cleat, to prevent planted feet from getting stuck when performing cutting, twisting, or jumping motions.
Stay tuned for Part 2 of this series, where I will talk about a few exercises for ACL prehabilitation or rehabilitation.
Figure 1: Sex Differences in Females Compared to Males
|Anatomical Differences||Muscular and Neuromuscular Differences||Laxity and Range of Motion|
|Wider Pelvis||Diminished muscular force||Greater range of motion|
|Increased flexibility||Dependence on quadriceps muscle for stability||Genu recurvatum (knee hyperextension)|
|Less-developed ACL||Longer time to develop force||Increased knee laxity|
|Smaller ACL in size||Longer electromechanical response time||Increased hip mobility/rotation|
|Increased genu valgum (knock knee position)|
|Increased medial tibia rotation|
Wilk, K.E; Arrigo, C. Rehabilitation after anterior cruciate ligament reconstruction in the female athlete. Journal of Athletic Training 1999;34(2):177-193
- G.D. Myer, K.R. Ford, and T.E. Hewett, 2008, “Tuck jump assessment for reducing anterior cruciate ligament injury risk,” Athletic Therapy Today 13(5): 39-44.
- Wilk, K.E; Arrigo, C. Rehabilitation after anterior cruciate ligament reconstruction in the female athlete. Journal of Athletic Training 1999;34(2):177-193
- Noyes, F. R.; Barber, S. D.; and Mangine, R. E.: Abnormal lower limb symmetry determined by function hop tests after anterior cruciate ligament rupture. Am J Sports Med, 19(5): 513- 8, 1991.
- Pearl AJ. The Female Athlete. Champaign, IL: Human Kinetics Publishing; 1993:302-303.
- Lindenfeld TN, Schmitt DJ, Hendy MD, Mangine RE, Noyes FR. Incidence of injury in indoor soccer. Am J Sports Med. 1994;22:364-371.
- Ferretti A, Papandrea P, Conteduca F, Mariani PP. Knee ligament injuries in volleyball players. Am J Sports Med. 1992;20:203-207.