Anterior Cruciate Ligaments: Defined

The Anterior Cruciate Ligament tear is one of the most common and devastating injuries that can occur to an athlete. Any person who has been associate with athletics has or will be very likely to come across one if not something similar to this type of injury (i.e. sprains). According to Barry P.Boden of The Physician and Sports Medicine Journal, "Each year in the United States there are approximately 250,000 ACL injuries, or 1 in 3,000 in the general population (1). Assuming that at least one third of ACL-deficient patients require surgery, at about $17,000 per reconstruction, the estimated annual cost is about $1.5 billion (2,3)."

However, the common persons of the world (no offense intended) aren't usually as informed or familiar with the dreaded injury as those who have seen it first hand. So with that, I'll use this post to for at least a basic provider to those who don't fully understand the information surrounding the anterior cruciate ligament, what it does, and how it is injured.

So, What is the anterior cruciate ligament?


To put it simply, the anterior cruciate ligament (more commonly referred to as the ACL) is one of 4 major ligaments in the knee that helps prevent excessive movement within the knee joint.

NOTE: The knee technically is the most unstable joint in the body due to its imperfect structure of basically 2 bones sitting on top of each other.

The ACL, or anterior cruciate ligament, is an important ligament located inside the knee joint, which acts as

the primary stabilizer preventing forward displacement of the lower leg upon the thigh bone.

It also assists in the function of preventing excessive rotation and twisting in the knee. So think of it like 1 of 4 ropes that holds the bottom pole to the top pole. However, due to its structure of originating in the back of the knee and inserting into the front, it is the most important of the ligaments since when we stand up, the femur slides on the tibia in which the ACL acts to prevent excess movement beyond that.

So how do the injuries usually occur?

Over the course of the last year, basketball has seen a large amount of ACL tears especially to some of its bigger named players such as Ricky Rubio, Lou Williams, Derrick Rose, Iman Shumpart, and most recently Rajon Rondo. Its obvious how a contact ACL injury would occur as it is a detrimental force acted upon very vividly. But what about non-contact ACL injuries?

Much to the surprise of many patients, this important structure may be torn without a contact injury but rather

may occur simply with a sudden stop, hyperextension or twisting injury of the knee. Sports, such asbasketball,

that call for the foot to be planted followed by a sudden change in direction have a high incidence of ACL tears.

This can be very easily seen in the injuries occurring to Derrick Rose and Iman Shumpart. Rose performed a move that he routinely (and many other basketball players for that matter) performs on the court in which he came to a jump stop after accelerating. He has performed this move countless times, however, the last time he executed it, he suffered the injury to his ACL. The consensus thought at the time was that he tore it because of fatigue. There was 1:10 left in the 4th quarter of Game 1 of the playoff game against the 76ers. Could it have been worn down because of the amount of time he was in?

Before I answer that, I want to take a look at Iman Shumpart injury as well. Iman performed a less arduous basketball move than Rose's. It was more of a routine crossover move where he planted his foot in the open court and tried to cross over behind his back. As you can see in the video afterwards, he was in very, very much pain. As it would later be discovered, he too tore his ACL, but also managed to tear his meniscus. But how is it a move that looks so simple and is even more ubiquitous than Rose's jumpstop could cause so much damage?

And here is where the dispute of fatigue comes in. Rose tore his ACL in the 4th quarter in the final minutes. Rose is a starter and played starter minutes at a total of 37. Shumpart is (was) a bench player who was only on a total of 19 minutes and tore his in the middle of the 3rd quarter. Also, you could make the case that Shumpart's injury was more detrimental since it involved the tearing of the meniscus. So what gives?

How it works is, you have to observe how each player acquired their injury about their movements (or lack thereof), or in medical terms, determine the "MODE" of injury.

It’s known that ACL injuries occur in 3 a variety of ways. In a 5 year study conducted by Medvecky et al., 84 women basketball players were followed and an alarming 93% of all the ACL injuries diagnosed were from non-contact mechanisms. Non-contact mechanisms must involve anterior sheer of the tibia in relation to the femur. The quadriceps can produce significant anteriorly directed forces on the tibia, especially in the area of 0 degrees to 40 degrees of knee flexion. The magnitude of the quadriceps’ force can be influenced by the muscle size, the degree of central nervous system activation, and the velocity of movement. In addition, eccentrically loaded muscle can develop much more force than muscle that is shortening. These factors can theoretically produce enough force to tear the ACL. The most likely mechanism causing this isolated tear is extension and internal rotation of the tibia on the femur.

This is consent with Rose's MODE of injury. Rose accelerated as he usually does when he is driving the ball; from there, he proceeded to perform a jump-switch, if you will, with his body and which he did around a 90 degree turn and slightly jumped into the air and landed on both legs. When he landed, his legs were slightly bent and he had come to a near complete stop. With this, the momentum that he created with the acceleration caused a "loading" force to be sent through his legs in order to cope with the force that his speed and body generated. As seen afterwards, he immediately felt awkward after the jump and fell to the floor.

Shumpart's injury was a bit more hard define since he didn't generate as much force as Rose did. However, he apparently caused enough to cause his ACL and meniscus to tear. His mode was simply dribbling down the court; when he encountered the defender, he did a simple plant on his left leg to cross the ball over behind his back to the right and in turn, caused his ACL to tear.

So what causes the ACL to tear?

The simplest and most blatant answer to this? Simple pure -- bad luck. Now that isn't a medical definition, but that really what you could chalk it up to.

From Fig. 1, it can be gleaned that noncontact ACL injury likely occurs from combined loading to the knee joint [14–17]. This suggests that non-contact ACL injury possibly occurs when many risk factors and extreme conditions happen simultaneously. Non-contact ACL injury is also a whole body phenomenon that is best analyzed by simultaneously addressing multiple risk factors of which neuromuscular control, joint kinematics and geometry, as well as, external forces that may be the most important.

Numerous theories have been suggested to explain this problem. Many of these theories include both

extrinsic and intrinsic factors. Intrinsic factors would be considered uncontrollable, and would include greater

physiological rotatory laxity, smaller size of ACL associated with smaller intercondylar notch, valgus

malalignment, hyperextension, diminished proproception, leg dominance, quadriceps dominance, hormonal

influence, postural alignment, etc. Extrinsic factors would be considered potentially controllable. These

include decreased strength and conditioning, inappropriate shoes, motivation, deceleration forces during

injury, neuromuscular control, and body movement.

Barry P. Boden even tries to break it down by naming variety of factors such as Hormonal reasons (i.e. estrogen), Anatomic Inconsistencies such as ACL size, Intercondylar notch, Lower-leg alignment, Knee joint laxity, Muscle flexibility; and finally Environmental influences such as Playing style, Shoe-surface interface, and Uneven playing surface.

The truth is, there is no definitive reason behind ACL tears. So those who were blaming fatigue as a reason for Rose's ACL tear, you weren't wrong necessarily--just not all the way right. Fatigue could have very well played a factor, but that's what it is, A factor, and not THE factor. The reasoning behind non-contact ACL tears is about as much of a medical mystery as you can get. As are most non-contact ligament tears in the knee.

Can ACL tears (injuries) be prevented?

Most preventive strategies aimed to decrease non-contact ACL injuries refer to training programs [24]. There

is a lack of studies assessing the role of ground and shoe–surface interaction modifications to prevent non-

contact ACL injuries. Despite some authors reported that prophylactic knee braces reduced non-contact ACL

injuries in football players [71], others found contradictory data [67, 71, 74]. Thus, it is difficult to recommend

knee braces to prevent non-contact ACL injuries until higher quality studies are reported. Prevention

programs have focused on neuromuscular training methods to change modifiable neuromuscular and

biomechanical risk factors [11, 12, 28, 35, 41, 49, 53, 60, 62, 80] and to reduce the non-contact ACL injury

rates [9, 14, 20, 27, 31, 39, 44, 61, 72, 73]. Also, some consideration on the prevention of non-contact

ACL injuries in ACL reconstructed patients has been placed, despite only a few studies were conducted in

this field.

Any information that you find on prevention methods for ACL injuries will probably be very little on info and very irresolute in the definitive effects of it. Reason being, how can you prevent something that you truly don't know why occurs in the first place? As we've all seen with Rose, he loads his legs down with numerous amounts of padding, however, that can only prevent what occurs externally. So to be honest, everything is debatable as to why it occurs. Now one can obviously do the normal exercise one does to strengthen the legs (lifting, running, balance, stretching, etc.) and that should provide even the slightest amount of help in preventing some issues such as fatigue, weakness, lack of coordination, etc. As of now though, there is much research that needs to be done in order to assess this common issue. Hopes that studies will grow in the future will allow for more prevention and less occurrence of this detrimental injury.

Hope this post helped at least give you a basic idea of what's going on. Sorry, I'm not very good at making articles or explaining things all that well.

Here are my sources if you wish to have more in-depth and more experienced outlooks and studies from experts:

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