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Signs You Have Sustained An Injury To Your Knee Ligaments (ACL & MCL)

Signs you have sustained a knee ligament injury - ACL and MCL

Back then in my preclinical medical school days, anatomy was one of the very difficult courses. Not as though it was really that difficult but it requires a level of acute memory. You need to be able to find a way to describe what you see with your eyes on a daily basis. Even worse, how about those things you cannot see normally? Well, there was a provision of a human cadaver for dissection, but this is a story for another day.

Ligaments are structures in the body that connect one bone to another. They are important for the movement and support of the bones and by extension, the entire body. However, because of the critical position (between two extremely dense body structures - bones), ligaments are prone to several injuries. Also, they are not as dense as bones so they are more commonly associated with tear injuries.

The knee ligaments

The knee ligaments are some of the important structures that support the lower limbs and the movements of the legs and thigh to varying degrees, thus any injury to them will not only cause you serious pain but also limit your movement capabilities. The knee ligaments are four in number - two collateral ligaments and two cruciate ligaments - the Anterior Collateral Ligament (ACL), Medial Collateral Ligaments (MCL), the Anterior Cruciate Ligament (ACL) and the Posterior Cruciate Ligament (PCL).

The Knee Ligaments

Which injuries can be sustained by the knee ligaments?

Injuries of the knee ligaments include wear, tear and sprain. These injuries can affect any of the four ligaments listed above. Of the four knee ligaments mentioned, the anterior cruciate ligaments, followed by the medial collateral ligaments are the most commonly injured knee ligaments. Hence, you are going to learn from this article about the signs that you may have sustained a tear injury to these ligaments - the Anterior Cruciate (ACL) and the Medial Collateral ligaments (MCL).

Tear injuries of the knee are common and often results from abnormal movements that cause excessive strain on the ligaments following which the fibres give way. They can also result when there is a dislocation of any of the bones attached to them across that joint. A joint is where two or more bones meet. In dislocation, a bone leaves its joint due to external forces that are strong enough to overcome the resistance offered by the ligaments and supporting structures. This also leads to strain of these ligaments which may result in a tear.

Tear injuries of the knee ligaments are particularly important because first, they indicate severe injury to the knee ligaments. Also, tear injuries of the cruciate and collateral ligaments are not easily recognizable, even to the person who sustained the injury because the ligaments are covered by skin. However, certain clinical and sub-clinical signs can be used to detect any serious injury to the knee's most commonly injured ligaments (the ACL and MCL).

Who is more prone to ACL and MCL injuries?

Because of their position (around the knee joint), injuries to the knee ligaments are commonly experienced among people involved in contact sports like football, basketball, those who frequently have a need to move the legs over great angles like tennis players, sprinters and other athletes.

ACL and MCL and Signs You May Have Sustained Injuries To Them

Anterior Cruciate Ligament (ACL)

ACL is a ligament in the knee that crosses from the base of the femur(thigh bone - longest bone in the body) to the top of the tibia (the largest bone in the lower leg). It connects the two bones at the knee joint, supports them and aid movement. It is primarily responsible for preventing the sliding of your tibia over the front of your femur and for controlling rotation across the knee joint.

Connecting two of the strongest bones in the body, you'd expect more injuries to the Anterior Cruciate Ligament and one of the common ways this can happen is when you engage in sports activities like running, football, rugby and some of the ones I already listed above.

Most ACL injuries can be very serious and often requires surgery to fix. However, a few cases of mild ACL injuries may only require rest and rehabilitation exercises designed to help you regain strength and stability.

Signs you may have sustained an ACL injury

While the severity of ACL tears may vary from patient to patient, there are some signs that may suggest that you have sustained an injury to your Anterior Cruciate Ligament. Here are some common signs you should look out for.

1. A pop sound: Individuals who experience ACL tears hear a clear "pop" at the time the injury happens. This sound can be so loud that individuals in the surrounding area may hear it. The pop sound is often followed by an immediate shift in the knee joint.

2. An unstable knee: Since the ACL plays a key role in the movement and stability of your knee, an injury to this ligament will result in its instability. So, if after a collision you discover that your knee has suddenly become unstable, there are high chances are that you may have torn your ACL.

3. Pain in the knee: Injury to the ACL is often followed by a shift in the knee joint, and as you expected, pain in the knee. The pain is often a result of the inflammatory processes that follow the injury and rupture of blood vessels in that area. This also presents as the joint swelling and redness of the soft tissues in that area.

Medial Collateral Ligament (MCL)

The medial collateral ligament (MCL) is a broad, thick band of tissues on the inner aspect (medial aspect) of the knee joint that connects the base of the thigh bone to the top of the tibia. Its main function is to stop the leg from protruding too far inward. In addition, this ligament keeps the knee stable and allows it to rotate.

MCL injuries are also common, although not as common as ACL injuries. Injuries to the Medial Collateral Ligament occur when the ligament stretches too far due to external forces from the side of the knee joint. This may result in a tear that may be partial (through a section of the MCL), or complete (transversing the entire width of the MCL). 

A severe or complete MCL tear will require surgery by a knee surgeon. However, a mild MCL tear may be managed using basic supportive treatments like applying ice or cold pack, analgesics, and resting or immobilization of the limb until healing is complete.

Signs you may have sustained MCL injury

1. A pop sound: Just like an ACL tear, a tear in the MCL also produces a popping sound, more like a tear in a tensed band. Individuals who experience MCL tear often do not miss hearing this and if you do hear a popping sound from your knee, you should know that you may have sustained an injury to any of the knee ligaments.

2. Pain: For both ACL and MCL tears, pain is a constant feature. This pain may be mild or severe, depending on the extent of the tear or injury.

3. Knee stiffness: Knee joint stiffness is another finding in MCL tear you should watch out for. When your MCL gets injured, your knee joint gets swollen, resulting in knee stiffness. This further compounds the impairment of function already caused by the damaged ligament. It becomes increasingly difficult to move, straighten or bend your knees.

What To Do When You Sustain A Knee Ligament Tear

The interventions for knee ligament injury depends on the severity of the condition. Knee ligament injuries (tear/sprain) are classified into three grades based on severity;

  1. Grade I injury (mild)
  2. Grade II injury (moderate)
  3. Grade III injury (severe)

Grade I

Grade II

Grade III

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Mild and moderate injury

For mild and moderate ligament strains, the following supportive remedies can suffice:

  • Rest and elevate your knee
  • Apply ice or cold pack
  • Avoid activities for at least six weeks after which full healing may have occurred
  • Compress your knee with an elastic bandage or tape
  • Use anti-inflammatory painkillers such as ibuprofen or acetaminophen to ease the pain
  • Use a knee brace to help provide support and stability

In addition to the above, the service of a health physiotherapist will be required to facilitate the healing process and help restore the normal functions of the ligaments to the pre-injury state as much as possible, and also reduce the risk of future knee ligament injury.

Severe injury

For severe knee ligament injuries or grade III sprains, surgery may often be required surgery, especially when it is your ACL or PCL that were involved, or if multiple ligaments were torn. Management of this type of knee injury will involve seeing a recommended orthopaedic surgeon who will thoroughly discuss the options with you.

In some cases, reconstructive knee surgery may be required. Complete recovery from reconstructive knee surgery takes six months or more but many people have been reported to return to the same or nearly the same level of activity and functionality as before the injury.

An alternative to knee surgery involves the use of a custom knee brace that helps to immobilize the joint and enhance its stability while it heals.

Other Knee Ligaments

I talked intensively on the injuries to the Anterior Cruciate Ligament (ACL) and Medial Collateral Ligament (MCL) in this article, but the other knee ligaments are worth mentioning. Let's see a few things about the Posterior Cruciate (PCL) and Lateral Collateral Ligament (LCL) in the following section.

Posterior Cruciate Ligament (PCL)

The PCL is the strongest ligament in the knee and therefore the least likely to sustain injury. It connects the base of the femur (thighbone) to the top of the fibula (lower leg bone) behind the knee joint and is responsible for controlling the backwards motion of the knee (flexion). A PCL injury occurs when that ligament is stretched or torn and is often called an "overextended knee".

Lateral Collateral Ligament (LCL) Injury

The LCL connects the base of your femur (thighbone) to the top of the fibula on the outer aspect of your knee. It provides stability to the outside of your knee, and a stretched or torn LCL compromises this function.


AS obvious as the signs that you may have sustained a knee ligament injury, you could still totally miss it altogether. Knee pain, popping sound, stiff joint, loss of movement of joint, are telltale signs that one may have sustained a knee ligament injury. Failure to recognise these signs or detect the tear could lead to a worsened situation. Hence, it is important you are able to recognise these signs and to watch out for them, especially if you are an active athlete.

Prosper Yole

I am a lifestyle blogger, I write useful articles on successful life tips and hacks. Posts bearing Prosper Yole as author are either written by the blog author himself or by our various other contributors. Thank you for reading through. I look forward to having you more often. Please subscribe to my blog and follow me on Twitter @ProsperYoleOfficial


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