Dienstag, 5. September 2017

The Cruciate Ligaments

After two long semesters at the University in Krems I was glad that summer break had begun. One thing was clear: I wanted to take one month to concentrate only on training. The plan was to focus on Kickboxing, but I totally fell in love with Luta Livre and spent most of my time learning about positions, escapes, passes and submissions. Soon I stumbled upon a technique called „Heel Hook“, a submission which attacks the anterior cruciate ligament (ACL). Pretty complicated stuff, so while at class I was trying to understand how to actually do and defend against this submission, after class I was part of some interesting discussions about the cruciate ligaments. Eventually I realized that I may not know as much about them as I thought I would. Therefore, I wanted to do a blog post about the knee joint, focusing on the cruciate ligaments, because I had found some interesting things during my research I didn't know before.

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So let's start with some basic anatomy of the knee: this joint is made up of three bones, the femur, the tibia and the patella. Between the tibia and the femur there are two „shockabsorbers“: the medial and lateral meniscus. They transfer the load from the upper leg to the lower leg and stabilize the knee. As you can see on the picture, the femur and the tibia have different forms. The mensicii build a link between those two bones so that they can fit together.
On each side (medially and laterally) there is a ligament called collateral ligament. The medial meniscus is grown together with the medial collateral ligament, which makes injuries in this region more complicated. The collateral ligaments give side way stability to the joint. Between the two condyles of the femur and attaching to the tibia, two ligaments cross each other – the anterior and posterior cruciate ligament. Their function is not that simple, so later on I will talk about them more detailed. But first let's talk about the movement directions, because they are pretty simple. The knee can be flexed and extended but can be rotated only very little.

Here are two helpful videos, where you can get a visual impression of this joint and it's characteristics:

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The ACL resists anterior tibial translation and rotational loads. The PCL is much broader and stronger than the ACL and helps to stabilize the knee. Usually people say, that the cruciate ligaments are taut in flexion and relaxed in extension. But unfortunately it's not that simple. The ACL is built up on one hand of a smaller anteromedial bundle which is tight in flexion and is the primary restraint against anterior tibial translation in flexion. On the other hand the ACL consists of a larger posterolateral bundle which is tight in extension and stabilizes the knee near full extension.
Although at approximately 30 degrees of flexion neither of the bundles are taught. This leads to the most translation available and is the position where injuries in twisting movement most likely occur. Generally speaking the problem with ligaments is, that they do not stretch like tendons do. Imagine ligaments as ropes and tendons as rubber bands for example. Stretching a tendon is part of everyday life. But if a ligament gets stretched too much it tears apart.

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Let's keep it simple and focus only on the ACL. Injuries of the ACL are very common in the field of sports and much more likely than PCL injuries. In sports cutting or sidestep maneuvers have a lot of impact on the ACL. These movements can be found a lot in soccer games or american football for example. The typical injury occurs with the knee externally rotated, in 10-30 degree flexion with the knee placed in a valgus position. ACL tears also occur, if there is an anterior tibia translation with the knee in shallow flexion.
Up to 80% of the ACL injuries occur in non-contact situations, for example if the athlete takes off with the aim of changing direction, or in landing situations, with the knee close to full extension. Especially landing situations require eccentric muscle action. If the hamstrings and the quadriceps are weak, the tibia translates anteriorly and the ACL might get injured. 

The Heel Hook on the other hand is a little bit different, because it is a contact and not a non contact situation. During this submission internal rotation on the tibia is applied via the heel. Also in flexion the tibia acts as long lever arm that generates increased forces to the joint. As we have heard before flexion combined with internal rotational forces are very dangerous for the ACL. So if a fighter finishes this submission and the opponent doesn't tap in time, or the fighter is not cautious enough, the ACL of the attacked fighter will be torn apart. Therefore, the Heel Hook is known to be a very dangerous submission and is even forbidden in some competitions. During training sessions I haven't had any troubles with the Heel Hook, because if you know about its dangers and are cautious in training sessions then injuries shouldn't happen at all.

There are ways to prevent ACL injuries. A lot of exercises in the field of prevention are focusing on balance training, plyometrics, movement education and agility training. Next semester at University I will attend to a lecture about sport specific injury rehabilitation. Hopefully I will learn about this pathology and its rehabilitation a lot more, so I can tell you about it in another blog post.


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