Knee Medial Collateral Ligament Sprain

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Knee Medial Collateral Ligament Sprain

The medial collateral ligament (MCL) plays a crucial role in resisting valgus stress, contributing more than half of the resistance when the knee is fully extended and approximately three-quarters when the knee is flexed to 25 degrees. When the knee is fully extended, the posterior portion of the MCL is subjected to the greatest strain at its femoral attachment under valgus load. Other structures that assist in resisting valgus forces include the anterior cruciate ligament (ACL), posterior oblique ligament, medial capsule, medial meniscus, and the semimembranosus muscle.

The most common mechanism of injury to the MCL involves a blow to the lateral side of the knee, causing the knee to buckle inward (valgus force). This type of injury is frequently associated with contact sports but can also occur in traumatic events, such as a car bumper striking a pedestrian. An MCL injury may also result from a valgus load combined with external rotation of the tibia, often seen during athletic activities that involve cutting maneuvers (sudden changes in direction with the foot planted) or abrupt directional shifts while skiing.

MCL injuries frequently occur alongside anterior cruciate ligament (ACL) injuries, as both share similar mechanisms of injury. In both cases, valgus stress is generated by a sudden change in direction or a collision impacting the anterolateral aspect of the knee, resulting in a combination of abduction (valgus) and hyperextension (recurvatum) forces. Because the deep fibers of the MCL are connected to the medial meniscus, injuries to the medial meniscus are also commonly seen in conjunction with MCL tears.

Grading

MCL injuries are classified into three grades based on their severity:

Grade I MCL Injury

• A mild injury where the ligament is stretched but not torn.
• The patient experiences some pain and slight swelling in the medial knee.
• The knee joint remains stable, with little to no impact on the range of motion.
• The Valgus Stress test shows minimal medial joint gapping (less than 5 mm) and a minor “Suction Sign.”

Grade II MCL Injury

• A moderate injury where the MCL is partially torn.
• There is usually more pain and swelling compared to a Grade I injury.
• The knee may be unstable and there could be some difficulty with weight-bearing and movement.
• The Valgus Stress test reveals a medial joint gapping of 5 to 10 mm plus a significant ‘Suction Sign’.

Grade III MCL Injury

• A severe injury involving a complete tear of the MCL.
• Significant pain and swelling are present, often accompanied by a “popping” sensation at the time of injury.
• The knee is notably unstable, with a high likelihood of buckling during weight-bearing activities.
• The Valgus Stress test shows medial joint gapping greater than 10 mm, along with a pronounced “Suction Sign.”

The following history findings vary based on the severity of the injury:

• Mild to severe medial knee pain, typically following trauma to the knee.
• Pain that worsens with weight-bearing and improves with rest.
• A “popping” sensation at the time of injury may be reported, particularly in Grade III injuries.
• Patients may notice mild to significant swelling in the medial knee.
• Knee stiffness is commonly reported in Grades II and III injuries.
• Knee instability is often present in Grades II and III injuries.
• Buckling of the knee during weight-bearing activities is a hallmark of Grade III injuries.

The following physical examination findings vary based on the severity of the injury:

• Difficulty walking, standing, or performing activities that require knee stability and movement.
• Ecchymosis (bruising) may be present, especially in cases involving tearing of the MCL.
• Mild to significant swelling on the medial side of the knee.
• Limited range of motion in both knee extension and flexion, depending on the severity of pain and swelling.
• Tenderness on palpation along the MCL.
• A positive Valgus Stress test, which may also reveal a “Suction Sign.”

Plain radiography can be helpful in ruling out an avulsion fracture of the MCL. While diagnostic ultrasound may assist in evaluating MCL tears, the preferred imaging modality is MRI. MRI not only provides detailed grading of MCL injuries but also allows for the assessment of concurrent damage to other soft tissue structures, such as the anterior cruciate ligament (ACL) or menisci.

The following are examples of red flags for patients presenting with knee pain:

• History of significant trauma or injury
• Severe or unrelenting pain
• Pain that occurs at night (nocturnal pain)
• Unexplained weight loss
• Fever
• Visible deformity
• Significant swelling
• Leg pain that develops after prolonged immobility or bed rest
• Neurological symptoms such as tingling, numbness, burning, or other impairments in the lower extremity
• Loss of leg pulses
• Substantial loss of range of motion
• Severe tenderness on palpation or intense pain with any examination procedure

If any of these red flags are identified during history taking and clinical examination, urgent referral for medical evaluation and further investigation is warranted.

• Heat or Cold? – Some practitioners advocate using moist heat in the subacute or chronic phase of a musculoskeletal injury. However, we have found that patients often benefit from the continued application of ice to reduce discomfort and manage inflammation. The application of ice helps to decrease the patient’s pain which then allows them to tolerate some movement. This helps the patient to maintain range of motion, stimulates circulatory perfusion, and prevents potential atrophy, all of which help to speed up recovery. 
• Best Time to Examine the Knee – The best time to examine the injured knee is within 2 to 4 hours following an injury (prior to the onset of muscle spasm). However, if muscle spasm is already present, it might be more appropriate to assess the patient after a 24-hour period of immobilisation.
• Structural, Inflammatory or Infection? – Structural knee problems generally cause pain with activity and are less painful (or painless) at rest, whereas knee inflammation or infection generally causes pain both with activity and at rest.
• Synovial Fluid or Blood? – Following knee trauma, if an effusion develops slowly within 24 to 36 hours, it most likely is due to excess synovial fluid. This is called synovial effusion. In contrast, if an effusion develops rapidly within 2 to 4 hours, it most likely includes blood. This is called haemarthrosis. Haemarthrosis indicates injuries such as a ruptured anterior cruciate ligament or intra-articular fracture and requires immediate medical attention.
• Patients with joint effusion characteristically keep their knee in a partially flexed position in order to maximise the joint volume, thereby reducing discomfort from the pressure.
• Medial or lateral knee pain accompanied by tenderness along the joint line can suggest potential meniscal damage or injuries such as ligament sprains or tears.
• Pes anserine bursitis frequently gives rise to medial knee pain which intensifies when the knee is flexed or extended.
• Adolescents with medial knee pain, with or without simultaneous hip discomfort, require investigation for a potential slipped capital femoral epiphysis.
• A full MCL tear may be less painful than a partial tear.

Mechanism of Impact Injury and Potential Structural Damage

When a direct blow (impact) to the knee occurs, the following indicators from the patient’s history can assist in knee pain diagnosis:

• A blow to the anterior hyperextended knee – Anterior cruciate ligament (ACL) injury
• A blow to the anterior flexed knee – Posterior cruciate ligament (PCL) injury
• A blow to the medial knee – Lateral collateral ligament (LCL) injury
• A blow to the lateral knee – Medial collateral ligament (MCL) injury

Differential Diagnosis of Knee Pain by Pain Region

Anterior Knee Pain

• Patellar subluxation or dislocation
• Tibial apophysitis (Osgood-Schlatter lesion)
• Jumper’s knee (patellar tendonitis)
• Patellofemoral pain syndrome (chondromalacia patellae)
• Myofascial pain syndrome
• Patellar dysfunction

Medial Knee Pain

• Medial collateral ligament sprain
• Medial meniscal tear
• Pes anserine bursitis
• Medial plica syndrome
• Knee joint dysfunction
• Myofascial pain syndrome

Lateral Knee Pain

• Lateral collateral ligament sprain
• Lateral meniscal tear
• Iliotibial band tendonitis
• Proximal fibular dysfunction
• Myofascial pain syndrome

Posterior Knee Pain

• Popliteal cyst (Baker’s cyst)
• Posterior cruciate ligament injury
• Knee joint dysfunction
• Myofascial pain syndrome

Medial Knee Pain Caused by Myofascial Pain Syndrome

In patients presenting with medial knee pain, a complete clinical examination should include an evaluation of the vastus medialis muscle to check for the presence of a myofascial trigger point as the concomitant or primary cause of the patient’s pain.

• The trigger points associated with myofascial pain syndrome may be located anywhere within a muscle and its fascia. Therefore, the entire muscle should be examined thoroughly. However, based on our clinical experience, the common location for the trigger point in the vastus medialis muscle is presented in the image below.

When Is Imaging Necessary?

In acute knee injuries, the ‘Ottawa Knee Rules’ can be used to determine when radiographic studies are necessary. According to these rules, radiographs of the knee should only be obtained after acute injury if patients meet one or more of the following criteria:

• Aged 55 years or over
• Tenderness at the head of the fibula
• Isolated tenderness of the patella
• Inability to flex the knee to 90 degrees
• Inability to bear weight both immediately and on clinical presentation

MRI is the best imaging technique for the diagnosis of soft tissue injuries of the knee such as meniscal and ligamentous injuries