ACL Tear and MCL Tear: Key Differences and Treatment Options for Individual and Combined Injuries

What is the difference between the ACL and the MCL?

The ACL is in the middle of the knee joint, originating on the femur and then extending forward to connect to the top of the tibia. The MCL is on the inner side (medial aspect) of the leg. As stated above, there are differences in their functions that are based on their locations. Of note, the MCL is an extra-articular ligament which means it is outside the actual knee joint. The ACL is in the middle of the knee joint and is an intra-articular ligament. This is important to understand because, in general, extra-articular ligaments (MCL) can heal sometimes on their own without surgery, while intra-articular ligaments (ACL) cannot.

How is an ACL tear different from an MCL Tear?

ACL and MCL injuries can have a lot of overlap in terms of symptoms. Both can be caused by athletic injuries or by everyday trips and falls. Both an ACL tear and an MCL tear can happen suddenly, be associated with a popping sensation, be painful, and have swelling.

An MCL injury will cause pain in the medial aspect (inside) of the knee. There may also be a clear point of maximal tenderness (the highest level of pain while pressing on the leg). MCL injuries may impact the range of motion of the knee and people may feel pain with any sort of torque on the knee, including something as minor as getting the foot caught on a blanket at night.

ACL injuries are often more tender on the lateral aspect (outside) of the knee. ACL injuries usually impact the range of motion of the knee, with most people having difficulty getting the knee to be fully straightened.

Combination ACL and MCL injuries are usually swollen with limited range of motion and tenderness around the knee. Bruising is not a common symptom of either ACL or MCL injuries.

Is an ACL or MCL tear more painful?

Pain is a common feature of both ACL and MCL tears. Location of pain can be helpful in distinguishing between an ACL and MCL tear – with an MCL tear causing medial knee pain and ACL often leading to lateral pain.

How can you tell the difference between an ACL and MCL injury?

This is often very difficult to know without imaging. The mechanisms of injury for the ACL and MCL overlap significantly. In addition, ACL tears with a concomitant MCL injury (either low grade or high grade) are extremely common. Very often, an ACL tear occurs and there is also a low grade MCL injury. In this situation, the knee is braced to allow the MCL to heal with conservative treatment and then the ACL tear is addressed once the MCL has healed. Less commonly, the MCL experiences a high-grade injury and needs to be surgically fixed along with the ACL tear.

What are the symptoms of a combined ACL and MCL tear?

ACL and MCL injuries often occur together. This is due to the mechanism of injury of the knee, involving both rotational forces associated with an ACL injury and a valgus force associated with an MCL injury. (Valgus force on the knee is when force on the outside of the knee causes it to bend inward toward the opposite knee.) This happens with all kinds of sports activity and is common in skiing. Symptoms can include swelling or water inside the knee, stiffness with pain and difficulty bending and extending the knee, tenderness on the inside of the knee, and difficulty walking.

Can you walk with a torn ACL and MCL?

Some people can walk normally after an ACL and MCL tear. Some people have pain, swelling, and stiffness and require crutches and/or a brace to walk.

What should I do if I think I injured my ACL or MCL?

The initial treatment should be rest, ice, possible NSAIDs, a knee brace to support the injured ligaments, and use of crutches. People often visit an ER or an urgent care center and are placed in a knee immobilizer. But this is not necessary for an ACL and MCL injury. The best brace option for this combination of injuries is a hinged knee brace that allows range of motion but stabilizes the sides of the knee.

What type of doctor treats ACL and MCL injuries?

The best doctor to visit with an acute knee injury is a sports medicine specialist. This will ensure you are able to get a good examination of the knee (ligament stability, range of motion, swelling, and location of pain). The examination may not give an exact diagnosis right away, but it can lead you in the right direction. It is important to get imaging of the knee including an MRI to evaluate which structures were damaged. If you visit an emergency room or urgent care center, it is still a good idea to follow up with a sports medicine specialist to get a more thorough evaluation.

How is an ACL or MCL tear diagnosed? Do I need an MRI?

ACL and MCL tears can sometimes be diagnosed by a physical examination. But, often, the knee is swollen and painful immediately after injury and for several days or longer. For this reason, a physical exam shortly after a knee injury may not be reliable. If the patient has experienced an acute injury and there is swelling inside the knee, an MRI is necessary to make an accurate diagnosis.

Can ACL and MCL heal without surgery?

There are opportunities for nonsurgical treatment for a combination ACL and MCL tear. Very often, an ACL tear will require surgery because it is a ligament inside the knee joint and these ligaments heal poorly on their own. The MCL, on the other hand, is a ligament outside the knee and has a very high potential for successful healing.

With a combination ACL and MCL injury, the first goal is to brace the knee and then restore range of motion. This period of time, generally ranging from 2 to 6 weeks, allows the MCL to heal and gets the knee in a good state to undergo successful ACL surgery.

Knees that are stiff, painful, and swollen after an injury are sometimes classified as ‘angry.’ This is because of the trauma the knee just experienced. Angry knees do not do well with surgery right away because they will get even more swollen, stiff, and extremely painful afterward in a process called arthrofibrosis. For this reason, knees need a period of time to recover from the injury and become less angry before surgery is performed. A knee is ready for surgery when it is mostly ‘normal.’ This means that the knee should have at least 0-120 range of motion easily and have minimal swelling. The 0-120 range – a common rehabilitation protocol – refers to 0 degrees while the knee is fully extended (straightened) to 120 degrees (almost fully bent.)

How long does it take for a torn ACL and MCL to heal?

The initial period of healing for an ACL and MCL injury is normally about 4 to 6 weeks. This includes a brace, physical therapy exercises, crutches, and letting the knee return to a normal range of motion. After this, the decisions about surgery should be made in combination with a physical examination of the stability of the ligaments and guidance from an MRI.

Posted: 1/13/2025

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References

• Shultz CL, Poehlein E, Morriss NJ, Green CL, Hu J, Lander S, Amoo-Achampong K, Lau BC. Nonoperative Management, Repair, or Reconstruction of the Medial Collateral Ligament in Combined Anterior Cruciate and Medial Collateral Ligament Injuries-Which Is Best? A Systematic Review and Meta-analysis. Am J Sports Med. 2024 Feb;52(2):522-534. doi: 10.1177/03635465231153157. Epub 2023 Mar 24. PMID: 36960920. https://pubmed.ncbi.nlm.nih.gov/36960920/
• Westermann RW, Spindler KP, Huston LJ; MOON Knee Group; Wolf BR. Outcomes of Grade III Medial Collateral Ligament Injuries Treated Concurrently With Anterior Cruciate Ligament Reconstruction: A Multicenter Study. Arthroscopy. 2019 May;35(5):1466-1472. doi: 10.1016/j.arthro.2018.10.138. Epub 2019 Mar 14. PMID: 30878328; PMCID: PMC6500749. https://pubmed.ncbi.nlm.nih.gov/30878328/

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