The Differences Between An ACL and MCL Tear

The Differences Between An ACL and MCL Tear

Knee injuries are very common among athletes and individuals with an active lifestyle. One of the most common sports injuries to the knee are tears in the ACL or the MCL. Very often we get questions about these, so this article serves to shed some light on the differences between the two.

The knee is a complicated joint. A number of muscles, bones and ligaments, along with the joint, work together to help you move. However, a tear in the ACL (Anterior Cruciate Ligament) or MCL (Medial Collateral Ligament) can restrict motion and function and keep an athlete away from sports for many months, even an entire season.

While the the two knee injuries sound similar, they are quite different. Being aware of the difference between the two can help you make an informed decision about the treatment option. Your orthopedic surgeon is likely to recommend surgery followed by physical therapy if you have an extensive tear in any of your knee ligaments.

Your knee joint is formed by:
  • three bones – the femur (thighbone), tibia (shinbone) and patella (kneecap)
  • four ligaments – the ACL, PCL, LCL and MCL, that connect the bones by acting like strong cords to keep the knee stable.
The collateral ligaments are the Medial Collateral ligament (MCL), which is on the inside, and the Lateral Collateral Ligament (LCL), which is on the outside of your knee. They control the side-ward motion of the knee and brace it against unusual movement.

The cruciate ligaments, Anterior Cruciate Ligament (ACL) and the Posterior Cruciate Ligament (PCL), cross each other in the front and back of the knee to form an "X". They control the back and forth motion of your knee.

The ACL keeps the knee stable and doesn’t allow it to turn too much. It also prevents the tibia from overextending itself. An ACL injury is typically the result of a sudden twist of the knee or a dislocation. The ACL tear typically occurs with a ‘popping’ sound, followed soon by pain and swelling, within an hour or two. Walking becomes difficult, the knee feels unstable and you may not be able to fully straighten your knee.

The MCL prevents the leg from extending too inward and allows the knee to rotate. MCL tears may occur during a strenuous activity, such as playing soccer. MCL injuries are often the result of the knee being hit directly on its outer side. This may stretch the ligaments on the inside of the knee too far, causing tearing.

When you experience an MCL injury, you may feel:
  • pain, swelling and bruising on the inside of the knee
  • knee stiffness
  • difficulty or pain while bending or straightening the knee
  • a feeling that the knee buckle or may give out
  • pain or difficulty walking, sitting down, rising from a chair or climbing stairs.

While both a torn ACL and a torn MCL exhibit similar symptoms, like pain, swelling and inflammation, the main difference between the two is that an ACL tear occurs with a distinctive ‘popping’ sound but an MCL tear does not.

Another difference is recovery. For an MCL tear, the recovery may take up to 8 weeks or more with rehabilitation. On the other hand, an ACL tear may require surgery and at least 6 months or more of rehabilitation.

It must be stressed that both ACL and MCL tears are serious injuries, despite what the difference in recovery period might suggest. Either of these injuries can only be thoroughly assessed and treated by an orthopedic surgeon. The first action you should take if you have any knee injury, is to contact an orthopedic doctor in your area.


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