Why do we Need Menisci and How Can They Help the knee joint?

The knee joint is the biggest and the most important joint in the human body. This is because it does two main functions:

  1-Transmits the weight from the upper part to the lower part of the body.

  2-Moves in many different directions and in many different angles.

These two functions require the knee joint to be flexible and stable at the same time. The medial meniscus is mainly responsible for the stability of the knee because it is fixed, while the lateral meniscus is mainly responsible for the flexibility because it is not as fixed.

Why does the medial meniscus need to be more fixed?

The medial meniscus is closer to the center of the body than the lateral one. That means it receives higher pressure thanthe lateral meniscus because of the gravity. In the figure below, the line shows the direction through which the body weight transmit to the ground. The line is closer to the medial meniscus than the lateral meniscus, which means that the medial meniscus deals with much higher pressure. This is why the medial meniscus is more fixed.

Transition of the body weight 

What makes the medial meniscus more fixed than the lateral meniscus?

The medial meniscus is closely attached to two fixed structures called fibrous capsule and medial collateral ligament. These attachments contribute to the stability of the medial meniscus. on the other hand, the lateral meniscus is not closely attached to stable structures which makes it more flexible.

The attachments of the medial meniscus to the medial collateral ligament 

This great cooperation between the medial meniscus and the lateral meniscus results in a very fixed and flexible knee.

The Anterior Cruciate Ligament and The Medial Meniscus

As mentioned in one of my previous blogs, the medial meniscus is made up of three parts; anterior horn, posterior horn, and peripheral border. The most part that is subjected to be torn is the anterior horn.  Current anatomical research reported that there is a relationship between the medial meniscus anterior root tears and the anterior cruciate ligament position.
The anterior horn was recently found to be highly subjected to detachment from its normal point of insertion during anterior cruciate ligament reconstruction surgery-the surgery to relink the anterior cruciate ligament back to its position after tears-.

           

Why doctors can't do it accurately?
Doctors and researchers don’t really have a baseline data for the exact locations of the insertion points of the structures of the knee that they can use to detrain the insertion point. When doctors try to reconstruct the anterior cruciate ligament after tears they don’t usually reinsert it back to its exact insertion point. The exact point of insertion is also not always clear by just looking at the site of injury. Added to that, the two knees of one person don’t always have the exact insertion points, which makes using the other knee as a baseline for the insertion point almost useless.

Anterior Cruciate ligament 

What is the result if the reconstruction was not accurately done?
Scientists believe that, if the anterior cruciate ligament wasn’t inserted back to the exact point of insertion a bad consequence is more likely going to happen. The tension will increase on the anterior horn of the medial meniscus, which in turn will increase the chances of tears of the anterior horn of the medial meniscus.

The tension is equally distributed among knee structures and any change of the location of any structure will increase the tension on at least one structure and decrease the tension on at least one other structure, which in turn lead to injuries many problems to the knee.

What should happen?
Researchers should do more research to collect data about the exact points of insertions in all the knee structures. This will help doctors to be more precise when doing reconstruction surgeries to knee structures.