The knee is responsible for bearing the weight of a vast majority of your body at any given time. Simultaneously, it is the reason we are able to perform flexions and extensions about the hinge. Built for structure and support as well as movement and finesse, the knee is a marvel of a joint.

With so many responsibilities, the knee relies heavy on its support system to allow it to stay strong and functional. To keep the hinge lubricated, the knee contains synovial fluid that acts as motor oil to a car. Just as the oil prevents gears and throttles from grinding into each other and causing mechanical failure, this fluid travels between bones to provide lubrication and prevent destructive friction. Little pillows known as bursa sacs are also filled with this incredible liquid.

These fluid filled sacs act as shock absorbers to the knee. They reduce the likelihood of the femur crashing into the lower tibia and fibula and help ensure that all the other parts of the knee remain where they should be.

Every machine needs measures in place to ensure that parts that shouldn’t be touching, do not touch at any point in the future. Little o-ring washers known as menisci or meniscus as its singular form, work to separate parts in the knee that shouldn’t touch. This helps to greatly reduce detrimental friction which could otherwise lead to arthritis. These rings also help to increase stability.

All of these parts, however, are just the supporting cast to the real stars of the show; the knee ligaments.

The Four Ligaments of the Knee

knee ligaments diagram

These four knee ligaments work together performing duties the others cannot. Without any of these bone connectors in place, the other will have to compensate for the loss and take on roles they are not made to do. This opens the door to further potential injury as the remaining working ligaments would have added stress and thus more likely to fail.

Before getting into exactly how knee ligament sprains occur and how to treat them, it is important to first learn what a ligament is and what makes them so crucial to knee stabilization.

A ligament is a tissue just as muscle is a tissue. The key of a ligament’s effectiveness as a support and mobility system lies in its specific composition. Ligaments are made of fibrous connective tissue. Connective tissue, as it sounds, serves to connect body structures together and to create a support that is a stabile as possible.

Bone itself is actually a type of connective tissue, but it’s clear that a ligament is not the same thing. What sets ligaments apart from other connective tissue is that it owes it fibrous nature to its dense collagen percentage that makes up a huge majority of its composition.

Tendons, like ligaments, are also a specialized fibrous connective tissue, but different in what they offer connective support to. A tendon connects a bone to a muscle, and a ligament connects a bone to another bone. These bones connected by the ligaments in the knee are the femur to the tibia.

Here are the four different ligaments of the knee featuring their location and responsibilities, as what happens if you were to sprain any of them.

Anterior Cruciate Ligament (ACL)

The ACL is found deep within the knee and connects the thigh bone (femur) to the shin bone (tibia). The ACL exists to prevent the lower tibia from hyperextending past the higher femur.

A sprain, which can be anywhere from slight over-stretching (Grade 1 sprain) to a slight tear (Grade 2) or even a complete tear (Grade 3). If an ACL were to be sprained in any capacity, the knee could buckle into itself as the tibia eventually slides up past the knee and pressing up against the femur.

knee xray

Posterior Cruciate Ligament (PCL)

You’ve probably heard the term posterior before and it means just about the same thing in all anatomical cases. Posterior means behind and it rests behind the ACL, crossing the other ligament and forming an X of stability with the femur and tibia.

The PCL’s job is to prevent hyper-flexion of the tibia to the femur. Although rare, it is possible for the knee to lose all stability and allow the tibia to slide all the way past the posterior side of the thigh bone.

PCL sprains are the least common of the four ligaments as excessive backwards motioning the tibia is a hard thing to do during any type of physical activity. The PCL is also guarded by the ACL from trauma to the front of the knee and boasts the strongest stability of the knee ligaments.

Medial Collateral Ligament (MCL)

The MCL is located medially to the knee, meaning it is along the midline of the body. The MCL as well as the LCL are actually located on the outside of the knee and work to connect the tibia to the femur and provide additional support to the knee.

The MCL’s main responsibility is to withstand blows caused to the opposite lateral side of the knee.

Lateral Collateral Ligament (LCL)

The LCL is located on the outside of the knee furthest away from the body. It too connects the thigh bone to the shin bone. Its main function, along with overall added support— is to withstand blows to the inside of medial side of the knee.


Knee Sprain Treatment

knee treatment

Damage to any of these four ligaments can send the knee on a sure path to a domino effect blowout of the other ligaments if not properly treated.

While a grade 1 or grade 2 sprain can usually be healed by means outside of the operating table, a grade 3 sprain, also known as a complete tear—almost always require surgery. This need for surgery arises because ligament, by nature, have a very poor blood supply.

If the need for surgery does arise doctors can work to tie the two loose ends of the ligament back together or anchor them back into the tibia or fibula if the injury occurs close to the bones.

If you were lucky enough to only suffer a mild to moderate grade 1 or 2 sprain, there are several approaches that can and should be used to increase the likelihood that it does not become a full tear.

The RICE method of injury treatment is a tried and true approach that can be followed with ease. RICE is an acronym standing for rest, ice, compression, and elevation.

R

Rest

I

Ice

C

Compression

E

Elevation

Rest is important because it allows the body time to heal itself, while also decreasing the likelihood of further injury.

Ice works to reduce inflammation as well as any pain. Ice can slow down blood flow away from the injured area and allows healing factors to stay with the area, which speeds up recovery time and sets the body up for a successful healing process.

Compression does a lot of the same things but can be utilized more frequently than ice as too much contact to the freezing surface can do damage to circulation. A compression sleeve or stocking can help get the blood where it needs to be.

Elevation of the leg past the heart can also greatly increase blood flow to the knee area, sending in white blood cells and other healers into the ligament faster than it can naturally.

Over the counter non-steroidal anti-inflammatories (NSAIDs) can help reduce pain to the area as well, but make sure only to use as directed, as overuse can lead to bleeding within the digestive tract.

Crutches can also be used in conjunction with the RICE method to lower the load put on the injured ligament.

All these approaches not only work to heal grade 1 or 2 knee sprains but can also greatly help prepare a grade 3 complete tear for surgery. Using RICE will lower inflammation to the affected area and make the surgery possible faster, in effect speeding up the healing process.

Key Takeaways from a Knee Sprain

A Knee sprain, regardless of grade severity, is not something to take lightly. If you are unlucky enough to experience one, it is very important to have a protocol in place to help heal the ligament and prevent future knee instabilities.

The RICE method uses rest, ice, compression, and elevation to help heal the damage to a grade 1 or 2 sprain.

A complete grade 3 tear usually requires surgery to correct but using RICE can significantly help speed up healing in this case as well.

 

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