ACL or MCL Injury: Know the Difference

ACL or MCL Injury: Know the Difference

Richard Kang, MD Blog

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ACL and MCL injuries both occur in the knee area. You may have heard of these terms before, as common knee injuries tend to involve one of these ligaments. Although they are both parts of the same joint, injuries to these ligaments are quite different in the cause, location, symptoms, and recommended treatment for each. Here’s what you need to know about ACL and MCL injuries.

What Does ACL Stand for?

ACL stands for Anterior Cruciate Ligament. The cruciate ligaments in the knee control the back and forth movement of the knee joint. The ACL crosses over the PCL (Posterior Cruciate Ligament), forming an X shape behind the patella (knee cap).

What Does MCL Stand for?

MCL stands for Medial Collateral Ligament. It is located along the inside of the knee. The LCL is the Lateral Collateral Ligament, which is on the outside of the knee. Together, the collateral ligaments control the side to side movement of the knee.

What is a Ligament?

Ligaments are the fibrous connective tissues that hold joints together. More plainly, ligaments are what hold bones together. Under normal amounts of stress, ligaments will keep a joint moving smoothly in proper alignment. You have ligaments in your knees, shoulders, elbows, ankles, wrists, hips, and other joints.

What Causes Ligament Injuries in General?

Injuries occur when too much stress is put on a joint. Excessive force or repeated stress over time can cause a ligament to tear. An example of excessive force would be a sudden injury like a fall or a blow to the area. Repeated stress over time refers to a tear from doing the same movement (work or athletics) over and over. Too much weight put on a joint over time can also cause an injury to a ligament. A ligament tear can be extremely painful, and takes a long time to fully heal.

What Could Cause an ACL Injury?

A sudden twist of the knee or a dislocation of the joint could cause a pull or tear of the ACL. This could happen anywhere, including playing a sport, while running, or during a car accident. It could happen at home, at work, at school, or anywhere in between.

How to Know If You Have an ACL Injury

If you feel a sudden pain under your knee cap or hear a loud popping sound, you most likely have torn your ACL. Pain is usually immediate and swelling occurs in the next few hours following the incident. Your knee may feel unstable, you may have trouble straightening your knee, and walking may be difficult or impossible.

What Could Cause an MCL Injury?

A blow to the outside of the knee can cause the ligament on the inside of the knee (the MCL) to stretch and possibly tear. This is more common when playing a contact sport such as football or soccer. It could also happen as a result of an accident where there is force applied to the outside of the knee.

How to Know If You Have an MCL Injury

You tend to feel pain on the inside of the knee when an MCL injury occurs. You may see some bruising on the inside of the knee and feel some stiffness. You may also experience difficulty bending or straightening the knee, walking, climbing stairs, sitting down, or standing up. The knee may feel weak, as if it will buckle at any moment. Unlike an ACL tear, there is no popping sound at the time of injury.

Treatment for ACL vs MCL Injuries

An ACL tear is more serious than an MCL tear, and may require surgery to repair. Recovery time may be 6 months or more, including rehabilitation. An MCL tear can take around 8 weeks to recover from, but surgery is usually not required.

Do You Think You Have an ACL or MCL Injury?

If you suspect you may have injured or torn your ACL or MCL, call CORE Medical & Wellness today: (888) 521-0688. There are a variety of non-surgical treatment options and rehabilitation services available to help relieve pain and restore range of motion to the joint. For more information about non-surgical orthopedic practices at CORE Medical & Wellness, visit:

Dr. Richard Kang is double board certified in anesthesiology and pain medicine, and he  completed an interventional pain medicine fellowship at the prestigious New York Presbyterian Hospital / Columbia University – College of Physicians and Surgeons.  Read his full bio here.