Anatomy & Definition

The Medial Collateral Ligament (MCL) is the primary ligament that provides valgus stability across the knee. The MCL is located at the medial aspect of the knee and begins at the medial epicondyle of the femur, crosses the knee joint medially, and then inserts approximately 4.5cm below the medial joint line onto the proximal tibia. An MCL tear or sprain occurs when a patient sustains a valgus stress to the knee, which causes the knee to buckle inward or medially. The injury mechanism typically occurs with a forceful blow or impact to the lateral side of the knee that causes the knee to buckle or rotate medially while the foot is firmly planted. This mechanism causes a distraction force to the medial structures of the knee, injuring the MCL. At the same time, a compression force to the lateral structures of the knee might also result in a concomitant injury (ex. lateral meniscal tear or lateral tibial plateau fracture).


The MCL injury is the most common ligamentous knee injury which accounts for nearly 40% of ligament injuries within the knee. These injuries most commonly occur in athletes. The mechanism of injury is most commonly from a direct blow from the lateral aspect of the knee with the foot firmly planted in the ground, which produces a high force of valgus stress across the knee. Not as common, other mechanisms of injury involve sudden twisting, pivoting, or cutting motions. Males are more often affected than females. The sports associated with an increased chance of sustaining an MCL injury are soccer, football, rugby, skiing, and ice hockey. Isolated MCL injuries can occur, however they are more commonly seen in multi-ligament injuries. An example of a common multi-ligament injury that involves the MCL is the “unhappy triad” which is injury to the MCL, ACL, and medial meniscus. Remember that the most common meniscal tear seen in association with the ACL tear is a vertical tear of the posterior horn of the lateral meniscus! However, a bucket-handle medial meniscus tear is part of the “unhappy triad.”


These injuries occur more commonly in contact sports than non-contact sports. The most common site of injury within the MCL is the proximal aspect at the femoral insertion, which has the highest chance of healing with conservative care. Isolated MCL injuries are graded from lowest to highest, grade 1 being the least severe and grade 3 being the most severe.


The patient typically reports some degree of valgus stress that was placed across the knee that was associated with relatively acute pain and swelling. Sometimes patients can recall a specific “pop” coming from the knee. Pain will be located at the medial aspect anywhere along the course of the MCL. Tenderness at any one specific attachment site can usually direct the physician to the direct site of the injury. The most common site is at the medial femoral condyle at the origin of the MCL. Tenderness across the medial joint line most likely indicates a mid-substance tear. The patient will also have trouble walking and difficulty taking their knee through full range of motion due to pain. On inspection there is a possibility of a knee effusion along with bruising seen at the location of the MCL. If a true MCL injury is present, the clinician will take the patient through a thorough physical exam which includes valgus stress testing of the MCL. A positive test is indicated with reproduced pain with the valgus stress along with possible laxity of the MCL depending on the degree of injury. The knee will be placed in 30 degrees of flexion and a valgus stress will be applied. Then, based on degree of opening, the grade of injury will be determined. Grade 1 is associated with pain on valgus stress with minimal opening, Grade 2 shows some mild opening of the joint medially, and Grade 3 usually has a large degree of opening along the medial aspect of the knee. The injured knee is compared to the contralateral uninjured side for grading. If there is laxity noted on full extension of the knee, this could be more indicative of a multi-ligament knee injury.


Routine radiographs will be obtained to rule out any fracture or avulsion type injury as well as other boney injuries around the knee. If clinically warranted and an additional soft tissue injury is suspected, such as a medial meniscus tear or ACL tear, an MRI can be ordered to better assess the integrity of the soft tissue structures within the knee and confirm or rule-out an MCL injury. MRI can best be utilized to provide an exact grade of the injury.


Treatment is primarily focused on conservative care, especially for Grade 1 -2 injuries of the MCL. Conservative care regimen usually consists of an NSAID to help control swelling and inflammation within the knee. Additionally, physical therapy will be ordered to help regain full range of motion within the knee and to aid in strengthening the knee to provide stability. Lastly, stabilization with a hinged knee brace is typically utilized for 6-8 weeks. Typical return to sport is seen around 6-8 weeks. There has been shown to be a 98% recovery rate for athletes who sustain a grade 1-2 injury that undergo conservative care.

Surgical intervention is rarely required for isolated MCL injuries. Surgery is primarily reserved for multi-ligament injuries or chronic isolated MCL injuries that have failed conservative care modalities with prolonged instability and valgus laxity on exam. Surgical intervention involves reconstruction of the ligament with an allograph tendon. This graft will be placed in the anatomic location of the MCL and will help provide stability across the knee. If an ACL or meniscus tear is also present, they will also be addressed during the procedure.

Dr. Dold performs MCL surgery and multi-ligament knee injury reconstruction. For more information on Dr. Dold and his practice, click here. To schedule a new appointment, click here.

Dr. Dold has published the first ever article in the Journal of the American Academy of Orthopaedic Surgery (JAAOS) on the structures of the posteromedial corner of the knee:

“The posteromedial corner of the knee encompasses five medial structures posterior to the medial collateral ligament. With modern MRI systems, these structures are readily identified and can be appreciated in the context of multiligamentous knee injuries. It is recognized that anteromedial rotatory instability results from an injury that involves both the medial collateral ligament and the posterior oblique ligament. Like posterolateral corner injuries, untreated or concurrent posteromedial corner injuries resulting in rotatory instability place additional strain on anterior and posterior cruciate ligament reconstructions, which can ultimately contribute to graft failure and poor clinical outcomes. Various options exist for posteromedial corner reconstruction, with early results indicating that anatomic reconstruction can restore valgus stability and improve patient function. A thorough understanding of the anatomy, physical examination findings, and imaging characteristics will aid the physician in the management of these injuries.” Andrew P Dold 1Stephanie SwensenEric StraussMichael Alaia; 2017 Nov;25(11):752-761.
Research and Related Articles