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Knee

MCL and PMC Injuries

The medial collateral ligament (MCL) is a vital structure located on the inner side of the knee. It serves a crucial role in stabilizing the knee by connecting the femur (thigh bone) to the tibia (shin bone). The primary function of the MCL is to prevent the knee from gapping open on the inside when force is applied to the outer side. MCL injuries are among the most common knee injuries, occurring two to three times more frequently than anterior cruciate ligament (ACL) tears.

The MCL spans the inside of the knee, providing structural support and controlling the knee’s side-to-side motion. It works to prevent the knee from buckling inward, a movement known as valgus stress. This ligament plays a critical role in maintaining knee stability during movements such as cutting, pivoting, or twisting. Because of its key role in stabilizing the knee, the MCL is highly susceptible to injury, especially in athletes involved in contact sports or activities requiring sudden directional changes.

The posteromedial corner of the knee is a region on the inner side of the joint that is responsible for maintaining knee stability. It consists primarily of two structures: the MCL and the posterior oblique ligament (POL). Both the MCL and POL work together to prevent valgus gapping, which occurs when the knee buckles inward under pressure. Additionally, they help control tibial rotation in relation to the femur, ensuring smooth, controlled knee movements.

The MCL provides stability when the knee is slightly bent (20-30 degrees of flexion), while the POL offers stability closer to full extension (0 degrees). This combination allows the knee to maintain stability through a wide range of motion, whether in everyday activities or athletic performance.

Reference: Posteromedial Corner Knee Injuries: Diagnosis, Management and Outcomes, A Critical Analysis Review. Cinque ME, Chahla J, Kruckeberg BM, DePhillipo NN, Moatshe G, LaPrade RF. J Bone Joint Surg Rev. 2017 Nov;5(11):e4. DOI: 10.2106/JBJS.RVW.17.00004.

MCL injuries can occur through both contact and non-contact mechanisms. One common cause of MCL tears is a twisting injury, where the knee buckles inward, leading to valgus gapping. Another common mechanism involves a direct blow to the outer side of the knee, which forces the inner side of the joint to open, placing stress on the MCL. Sports that involve frequent cutting, pivoting, or physical contact, such as soccer, football, and skiing, are particularly associated with MCL injuries. Each year, approximately 750,000 MCL injuries are reported in the United States alone, making it one of the most prevalent knee injuries.

The symptoms of an MCL tear vary depending on the severity of the injury, which is typically graded on a scale from I to III:

  • Grade I (mild): Pain is usually localized around the ligament attachments on the tibia or femur. There may be mild swelling and tenderness on the inner side of the knee.
  • Grade II (moderate): Swelling and pain are more pronounced, and the patient may feel instability or a sense that the knee is “giving out.”
  • Grade III (severe): The knee feels highly unstable, and there is significant pain, swelling, and difficulty bearing weight on the affected leg.

In more severe cases, patients often report that their knee feels unstable, especially during movements that require side-to-side motion or sudden changes in direction.

One of the unique characteristics of the MCL is its ability to heal on its own, particularly in cases of isolated MCL tears. This is due to the robust blood supply to the MCL, which provides the necessary nutrients and healing factors. Additionally, the MCL is located outside the knee joint capsule, which protects it from joint fluid that can inhibit the healing process. Unlike ACL injuries, which often require surgery, MCL tears have a much higher likelihood of healing without surgical intervention.

However, there are certain scenarios where MCL tears may not heal on their own. Two examples include:

  1. Valgus gapping in full extension: If the knee continues to gap open on the inside when fully extended, the injury may involve both the MCL and POL, reducing the chance of healing without surgery.
  2. Meniscotibial MCL tear: In this type of tear, the MCL detaches from its attachment on the tibia and retracts toward the knee. The ligament often becomes trapped above the hamstring tendons, preventing it from healing back to its original position.

In both of these cases, surgical intervention may be required to restore knee stability.

Accurately diagnosing an MCL or posteromedial corner injury involves a combination of physical examination, specialized X-rays, and magnetic resonance imaging (MRI).

One common diagnostic test is the valgus stress test, which involves applying pressure to the outside of the knee while the leg is extended or slightly flexed to assess the integrity of the MCL.

Specialized X-rays, such as stress X-rays, provide additional information about the severity of the injury. These imaging techniques allow physicians to objectively measure the extent of the damage and identify posteromedial corner injuries with millimeter accuracy.

The treatment approach for an MCL tear depends largely on the severity of the injury:

  • Grade I and II tears: These are often treated non-surgically with a combination of physical therapy and bracing. A well-structured rehabilitation program helps restore strength and stability to the knee, while a brace prevents further injury during recovery.
  • Grade III tears: These severe injuries typically require surgical intervention. The ideal time to repair or reconstruct the MCL and posteromedial corner structures is within the first two weeks after the injury, once the knee’s range of motion has been restored. This minimizes the risk of scar tissue formation and ensures that the knee heals in its proper anatomical position.

With advancements in surgical techniques, patients with Grade III MCL tears or multiple ligament injuries can often return to high-level physical activities following successful reconstruction.

Surgical reconstruction of the MCL and posteromedial corner focuses on restoring the native anatomy of the knee. Various techniques are available, including augmentation procedures, where a graft is used to support the patient’s own tissue, and full reconstruction, where grafts replace the damaged structures.

By accurately restoring the normal anatomical insertions of the MCL and POL, early range-of-motion exercises can be initiated during rehabilitation, leading to excellent long-term outcomes.

Recovery from an MCL injury or posteromedial corner surgery can take between 6 to 12 months, depending on the severity of the injury and whether other ligaments were involved. Physical therapy starts immediately after surgery, focusing on regaining range of motion while protecting the repaired or reconstructed ligaments. For the first six weeks, patients are advised to avoid weight-bearing or use crutches to protect the healing tissues.

After six weeks, a gradual, partially protected weight-bearing program begins. Patients may wean off crutches once they can walk without a limp. By the 7-8 week mark, most patients are cleared to drive. Rehabilitation progresses to include strength training and agility exercises, with most patients resuming sports or high-level physical activities between 9 to 12 months post-surgery.

Orthopedic surgeon Dr. Mark Cinque is a sports medicine surgeon in San Diego, California who specializes in the treatment of complex knee injuries. He has spent time training at The Steadman Clinic and Stanford Orthopaedic Surgery. He has published over 100 peer-reviewed manuscripts and has presented research internationally. He uses minimally invasive arthroscopic procedures to preserve the natural joint and reduce recovery time to accelerate his patients’ return to the activities they love.

At a Glance

Mark Cinque, MD

  • Board-certified, fellowship-trained orthopedic surgeon
  • Orthopedic Residency: Stanford University, Fellowship: The Steadman Clinic
  • Authored over 100 peer-reviewed publications
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