Description of an MCL Injury

The most common knee injury is to the medial aspect of the knee.

The medial collateral ligament, or MCL, extends from the end of the femur (thigh bone) to the top of the tibia (shin bone) and is on the inside of the knee joint. There are three main anatomic structures in the medial side of the knee, with the superficial medial collateral ligament being the largest and strongest. The other main structures are the posterior oblique and deep medial collateral ligaments. It is important to note that an MCL injury means that the entire medial knee structures are affected.

A large number of isolated medial ligament injuries are due to sporting injuries. An MCL injury can occur through stress against the outside of the knee that stretches or tears the medial knee structures. This injury can be caused through either contact or non-contact.

Symptoms of an MCL Injury

  • Pain directly over the ligament
  • Swelling and inflammation over the inside (medial) part of the knee
  • Severe cases patients will feel their knee “give out”, or buckle

Dr. LaPrade will examine the patient and use x-rays, stress x-rays, and in some cases, an MRI to evaluate the MCL area to determine the exact injury. An MRI shows the ligaments and muscles in addition to the bones, and it is very useful when determining if the injury is a partial or complete MCL tear and for which part of the medial knee structures are torn.

In order to verify if the MCL is in fact still partially intact or completely torn, Dr. LaPrade will perform a valgus stress test with the knee out straight and with the knee flexed to 30°. This test will check to see if the medial knee gaps open to side-to-side stressing. If increased gapping occurs, the MCL is most likely torn. To properly diagnose MCL injuries, doctors usually perform this test in combination or in addition to other physical exams.

Degree of MCL Injury

The grade of the medial ligament injury is based upon the amount of tearing present.

  • Grade I Injury: occurs when there is just slight tearing and no significant gapping
  • Grade II Injury: occurs if there is gapping present but an end point to valgus stressing at 30° of knee flexion.
  • Grade III Injury: occurs when there is a complete ligament tear of the medial side of the knee and stressing causes the lack of an endpoint. In chronic injury cases, a medial knee reconstruction will need to follow.

In general, most acute Grade I and II injuries will heal with a well supervised rehabilitation program. While the majority of isolated grade III medial knee injuries will heal, there are still some which do not heal and a grade III injury must be followed closely to be certain the patient does not have any problems with residual instability. In addition, it is well recognized having any “looseness” of the medial knee structures can cause an ACL graft to fail. Thus, when there is a combined medial knee injury and ACL injury, it is important to verify that the MCL injury heals completely prior to the ACL reconstruction or it should be concurrently repaired or reconstructed.

In the case of very severe combined knee ligament injuries, especially with a concurrent PCL tear, a concurrent medial knee injury should undergo a repair, augmentation repair, or a complete medial knee reconstruction.

How to Read an MRI of an MCL Tear

Treatment for an MCL Tear

Historically, the surgical treatment of medial knee injuries resulted in a significant number of patients developing postoperative stiffness, which often resulted in more surgeries for the patient. Thus, we have developed newer techniques in our research lab which allow us to have patients move their knee sooner to try and decrease the risk of stiffness and the necessity of secondary surgeries to treat their stiffness.

Dr. LaPrade has performed extensive anatomic, biomechanical, diagnostic and related studies to better understand the medial knee structures. Through this work, he has been able to develop an anatomic medial knee reconstruction procedure, which has been performed in patients and is currently undergoing clinical outcome studies.


In the acute medial knee ligament tear situation, patients are placed into a brace and are enrolled in an early rehabilitation program to emphasize quadriceps reactivation, edema control and knee range of motion. The main rehabilitation exercise for MCL tears is the frequent use of a stationary bike.

For isolated acute MCL injuries, most athletes can return to sports by multiplying the grade of the injury by two (in weeks) as a general time frame. Thus, a grade I acute MCL injury usually needs 1-2 weeks to heal, while a grade II injury takes 3-4 weeks to heal and a grade III isolated complete MCL injury typically takes 5-6 weeks of properly guided rehabilitation to have the injury heal completely.

The use of a hinged MCL protective knee brace is also commonly recommended in the acute situation when the knee is significantly unstable. Thus, we recommend the patient be fitted by one of our brace specialists. They will properly fit the MCL brace, which is durable enough for desired activity levels.

Related Studies

  • Anatomy of the Medial Part of the Knee
  • Medial Knee Part I – Static Function of the Main Medial Knee Structures
  • Correlation of Valgus Stress Radiographs
  • Management of Injuries to the Medial Side of the Knee
  • Structural Properties of Primary Medial Knee Ligament
  • sMCL – Anatomic Augmented Repair vs Anatomic Reconstuction
  • Analysis of Anatomical Medial Knee Reconstructions
  • Development of an Anatomic Medial Knee Reconstruction