MCL Injury Diagnostic Criteria

Access a helpful MCL Injury Diagnostic Criteria template for evaluating MCL injuries.

By Carepatron Team on Aug 2, 2025.

Fact Checked by Ericka Pingol.

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What is an MCL injury?

The medial collateral ligament (MCL) is a band of connective tissue on the inner side of the knee, bridging the femur (thigh bone) and tibia (shin bone). A common knee ligament injury, MCL damage is often the result of forceful twisting of the knee joint or direct trauma to the outer knee, as well as repeated stress and pressure over time from overuse. MCL injuries can be highly debilitating to the functioning of the knee joint. Athletes who play high-impact sports are at an elevated risk for MCL injuries.

Types of MCL injuries

MCL injuries range in severity from light sprains to a partial or complete tear of the knee ligament, with implications for recovery time and success. Typically, medical professionals classify MCL tears as Grade 1, Grade 2, or Grade 3 to indicate their severity (Reider, 1996):

Grade 1 MCL injuries are those in which 10% or less of the fibers that make up the ligament are torn. This type of mild tear is associated with some pain but little impact on knee stability. Grade 1 MCL injuries could heal on their own within a few weeks.
Grade 2 indicates a partial tear of the MCL has occurred. The severity of this kind of MCL tear depends on how many medial collateral ligament fibers are still intact.
Grade 3 refers to MCL injuries in which a complete MCL tear has occurred. Patients with a torn MCL of this severity display significantly increase medial laxity of the knee joint as very few connective MCL fibers are intact.

MCL Injury Diagnostic Criteria Template

MCL Injury Diagnostic Criteria PDF Template

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Signs and symptoms of an MCL injury

There are several key signs of an MCL injury. Like other knee injuries involving a torn ligament, MCL tears often result in a 'loose' or unstable knee joint. The patient might experience:

A 'popping' sound along with sudden and intense pain at the medial line of the joint at the time of the injury
Difficulty weight-bearing on the affected leg or feeling like their knee will collapse under their weight
Limited knee mobility or feeling their joint lock when they move.
Ongoing swelling, tenderness and pain at the site of the injury

Diagnosing an MCL injury

A physiotherapist or physician will need to perform a physical exam to determine whether the patient has injured their MCL or another part of the knee, such as the anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL). In severe cases, multiple ligaments of the knee joint may be damaged. A physical examination may need to be delayed until after the pain and swelling have subsided. Further tests may also be conducted, such as magnetic resonance imaging, X-rays, or ultrasounds, to determine the extent of the damage and to rule out bone fractures.

A physical examination first requires checking for pain and swelling at the location of the MCL (on the inner side of the knee). The examiner will perform a Valgus Stress Test at 30 degrees flexion, where the medial instability of the injured knee is compared to the non-injured knee. Medial laxity, or increased ‘gapping’ of the injured knee with side-to-side stressing, is a key diagnostic tool for determining the extent of MCL damage. This test is the best way to test the integrity of the MCL directly (Naqvi & Sherman, 2020).

Diagnostic criteria

Grade 1

Mild to moderate pain and tenderness on the medial side of the knee
Local swelling
No significant gapping under valgus stress

Grade 2

Moderate to severe pain and tenderness on the medial side of the knee
Local swelling
Looseness of the medial knee joint when pressure is applied
Medial knee gapping under valgus stress test, with an endpoint

Grade 3

Pain and tenderness of the medial side of the knee (note that in some cases, grade 3 tears will be less painful than grade 2 tears because there is little pressure on the severed ligament)
Significant swelling
Significant looseness of the medial knee joint when pressure is applied
Significant medial knee gapping under a valgus stress test, without a clear endpoint

Benefits of having an MCL diagnosis criteria template

Here are some of the key benefits of using our MCL Injury Diagnostic Criteria template:

Enhanced diagnostic accuracy

Initial diagnosis of an MCL injury is crucial as inaccurate assessments of the injury or its severity can result in delayed recovery. Using a diagnostic criteria chart makes it easy to differentiate grade 1, 2, and 3 injuries.

Convenience

This free MCL Injury Diagnostic Criteria makes it simple and easy to assess and document a patient's MCL injury symptoms.

Improved patient care

Having MCL injury diagnostic criteria on hand during physical examinations facilitates a comprehensive evaluation of the injury's severity, allowing assessors to easily tailor recovery advice and treatment plans to the patient's individualized needs.

Next steps after diagnosis

Initial treatment of MCL injuries includes resting and elevating the affected leg, and icing and compressing the injury to reduce pain and swelling. The patient may also need crutches for a time to keep weight off the injury and to wear a knee brace for stability. Prescription medication to manage knee pain may be necessary for severe injuries. The patient should be advised to avoid lifting heavy objects and not to play sports until their MCL injury has improved. Re-injury or overuse of a damaged ligament can prevent or delay a full recovery.

Physical therapy is also key to the rehabilitation process. The patient should make regular visits to a physical therapist, who will help to strengthen the injury and reduce knee instability. Regular assessments of the recovery progress should be made for a graduated approach to returning to normal function without exacerbating knee damage. With grade 2 and 3 MCL tears, surgery may be necessary.

Finally, many people with major knee injuries (especially professional athletes) experience psychological impacts as a result. It may be necessary to refer the patient to a counselor or sports psychologist to help them manage the stress associated with their injury and recovery.

References

Naqvi, U., & Sherman, A. l. (2020). Medial collateral ligament (MCL) knee injuries. PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK431095/

Reider, B. (1996). Medial collateral ligament injuries in athletes. Sports Medicine, 21(2), 147–156. https://doi.org/10.2165/00007256-199621020-00005

Commonly asked questions

Medial collateral ligament (MCL) injuries affect the band of tissue on the inner side of the knee that connects the femur to the tibia. MCL injuries occur when this ligament is partially or completely torn due to forceful external rotation of the knee joint or direct trauma to the lateral knee.

MCL injuries can typically be diagnosed during a physical examination, during which a doctor or physical therapist assesses a patient's pain, mobility, and medial laxity of the knee. When more severe MCL injuries are suspected, physicians typically conduct MRI or ultrasound scanning to assess the extent of the knee injury.

Grade 1 MCL injuries are less severe and will typically heal within a few weeks with adequate care as most of the connective fibers of the MCL are intact. Grade 2 indicates a partial tear of the MCL has occurred, while grade 3 indicates a severe or complete tear. These injuries take longer to heal, are associated with significant knee instability, and may require surgery.