If you’ve ever gone to a medical school or played a competitive sport, I’m 100% sure you’ve encountered this topic before

“What is your MCL and ACL?”

It’s a simple question about some of the most important ligaments in your knee. Both play a crucial role in stabilizing your knee joint. But when they are injured, it can be very difficult to effectively move through any range of motion, including walking, participating in sports, or other daily activities.

In this blog post, we will discuss what these ligaments are, what happens when they are injured, and how you can go about rehabilitating them. We’ll also provide some tips on how to prevent injuries to your MCL and ACL in the first place!

Anatomy of the Knee

The knee is a complex joint formed where the thigh bone (or femur) meets the shin bone (or tibia). The knee joint is held together by several ligaments, which help to keep the knee stable. It also contains a small amount of fluid, which helps to lubricate the joint and prevent friction.

Our knees are responsible for the things we do every day, including bending, straightening, and rotating. However, this flexibility also makes the knee susceptible to injury.

The knee is often damaged by sudden impacts or twisting motions. In addition, repetitive stress on the knee joint can lead to conditions such as arthritis. As a result, it’s essential to take care of the knee and seek medical help if it’s injured.

Four Major Ligaments

Four knee ligaments hold and provide stability to the knee bones. These ligaments are divided into two, collateral ligaments and cruciate ligaments.

Anterior Cruciate Ligament

The anterior cruciate ligament (ACL) is one of the four major ligaments of the human body. It’s located in the center of the knee, crossing from the femur (thighbone) to the tibia (shinbone). The ACL helps to stabilize the knee by preventing forward movement of the tibia relative to the femur. 

Posterior Cruciate Ligament

The posterior cruciate ligament (PCL) is a major stabilizing ligament of the knee joint. It runs from the back of the femur (thighbone) to the front of the tibia (shinbone) and crosses the anterior cruciate ligament (ACL). The PCL helps stabilize the knee by preventing forward movement of the femur relative to the tibia.

When the PCL is torn, it is usually the result of a direct blow to the front of the knee, such as in a football tackle or most prevalently a car accident. 

Medial Collateral Ligament

The medial collateral ligament, or MCL ligament, is a band of tissue that runs along the inside of the knee from the femur to the tibia. It helps to stabilize the knee and prevents too much knee valgus. The MCL is often injured when the leg is hit from the outside, which can commonly occur in sports.

Lateral Collateral Ligament

The (LCL) is located on the outside of the knee, and it attaches the thighbone to the fibula (the smaller bone that runs alongside the shinbone). The LCL helps to prevent the leg from moving too far out to the side or knee varus. It also helps to resist rotation at the knee joint. 


MCL vs ACL Injury

Many different types of knee injuries occur within the knee, and two of the most common are ACL and MCL tears. Both of these injuries can be quite debilitating and sometimes require surgery to repair. But what’s the difference between these two types of injuries?

ACL Tear

If you have a torn ACL, you know the feeling all too well. That sudden popping sound, followed by sharp knee pain, can be a real nightmare. Depending on the severity of the injury (or the grade of your tear), it can sideline you for months. An ACL tear is a very common injury in contact sports, such as football and soccer.

Symptoms of an ACL tear include:

  • pain,
  • swelling,
  • stiffness when moving,
  • and a feeling of instability in the knee when stopping.

MCL Tear

The MCL, or medial collateral ligament, is a ligament that runs along the inside edge of the knee joint. An MCL injury is often caused by a direct blow to the outside of the knee, such as in a football tackle. It also occurs when the knee is forcefully bent or twisted, resulting in a sharp pain on the inside of the joint. And in some cases, the MCL may completely rupture, causing the knee to give out.

Symptoms of an MCL injury include:

  • pain on the inside of the knee,
  • swelling,
  • and joint laxity.

Differences Between MCL and ACL

Magnetic resonance imaging (MRI) is usually used to diagnose the injury and determine the best course of treatment. While both ACL and MCL tears can cause similar symptoms, they differ in a few key ways.

  1. First, ACL tears are ligament tears that are much more common than an MCL tear.
  2. Second, ACL tears generally require surgery by an orthopedic surgeon, while MCL tears can often be treated with rest and physical therapy.
  3. Finally, while both injuries can be quite serious, ACL injuries tend to be more disabling than MCL injuries.

Treatment Options

There are four essential treatment options your orthopedic specialist may recommend after experiencing ACL or MCL injuries.

Physical Therapy

Physical therapy is often recommended to regain strength and mobility in the knee. A physical therapist will work with you to make sure he develops the ideal program you need to go through to ensure the proper recovery of your ligaments and knee joints overall.

Even after you have graduated from physical therapy, you usually have to spend time ensuring your joints are as strong as they were before the injury. This will take joint-specific training, which I have used for multiple years after my 4 knee surgeries.

Knee Brace

A knee brace is a device that is worn around the knee to provide support and stability. There are a variety of knee braces available, each designed to provide different levels of support. Knee braces are often used to treat or prevent injuries (although research confirming the latter is few and far between), such as an MCL tear or ACL injury. They can also be used to provide support after surgery so that the patient can comfortably start to progress to daily activities or sport-specific exercises.

Ice and Medication

You could also apply ice. Ice should be applied for 20-30 minutes at a time, several times per day. You can also take over-the-counter pain medication to help relieve pain and inflammation.


But if the injury is more severe, surgery may be necessary. The type of surgery will depend on the extent of the damage. Surgery typically involves making a small incision in the knee and repairing or replacing the damaged ligament.

Recovery time following surgery can vary depending on the individual, but physical therapy is typically required to regain the full function of the knee.


Have Hope

The recovery process for a ligament tear can be lengthy and challenging. That’s why it’s important to listen to your doctor and follow their instructions carefully. You’ll likely need to take some time off work or school to focus on your recovery.

Spending time with family and close friends during this time will also strengthen your mental fortitude and hope. After all, support systems are a game changer when it comes to healing from anything. You should also not feel alone during your recovery.

Many other people have been through the same thing and understand what you are going through. With patience and support, you will be able to recover from a ligament tear and get back to your normal life.

About the Author

Hi there! I’m Dr. Keagen Hadley, OTD, OTR/L. Straight out of the University of Mary, I’m all about blending my know-how in knee health, well-being, and medical technology. As a licensed occupational therapy doc, I’m here to translate complex concepts into clear, actionable insights – whether it’s knee care or groundbreaking healthcare tech.

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