A medial collateral ligament (MCL) tear or injury is a stretch, partial tear, or complete tear of the ligament on the inner inside of the knee. MCL is a band of tissue that runs along the inner edge of the knee connecting the thighbone to the lower leg bone. It is one of the most common knee injuries and results mostly from a valgus force on the knee (angular force pulling the leg outward).
MCL injuries often occur during contact sports. Direct contact to the outside of the knee during a collision can pull the knee sideways, which puts a lot of pressure on the MCL causing tears. Also, contracting the muscle while running and turning can exert enough stress on the ligament to tear it.
A tear or injury to MCL can be recognized by the following signs and symptoms:
What are the functions of the MCL?
The medial collateral ligament (MCL) is a big, broad, thick ligament on the medial side of the knee. It extends 1.5-2 inch from the inner part of the knee and the thighbone (femur) to the top of the shinbone (tibia). It is made up of a lot of collagen fibers and little elastic fibers. It connects the bones in the thigh and lower leg. MCL and the lateral collateral ligament (LCL), which runs along the outside of the knee, help to keep the knee in place. The main functions include:
- The MCL functions primarily to prevent the leg from bending too far inward.
- It is one of the four ligaments that are critical for maintaining the mechanical stability of the knee joint.
- It functions to control excessive motion by limiting joint mobility.
- It is also a source of proprioception (helps perceive the body’s position). It functions to resist forces applied from the outer surface of the knee and prevent the medial portion of the joint from widening under stress.
- The proprioceptors in the ligament monitor the position of the limbs in space and movements and the effort exerted to lift objects.
What causes MCL injuries?
Injuries to the medial collateral ligament (MCL) mainly occur when strong force hits the outside of the knee, lower thigh, or upper leg when the foot is in contact with the ground and unable to move. The ligament becomes stressed due to the impact and a combined movement of flexion and external rotation, which leads to tears in the fibers. These injuries are regularly seen in contact and noncontact sports and often occur in the following instances:
- When the knee is hit directly on its outer side, such as during a football tackle.
- As a result of cutting maneuvers, such as forcefully shifting the direction of the foot.
- Squatting or lifting heavy objects.
- Hyperextending the knee, such as in skiing.
- Repeated stress to the knee causes the ligament to lose its elasticity.
- Any direct blow. such as during a car accident.
Grades of MCL tears
The primary function of the medial collateral ligament (MCL) is to act as a valgus stabilizer (ensuring proper inward movement) of the knee. It is most often injured when external rotational forces are applied to the lateral knee, such as an impact to the outside of the knee. MCL injuries can be graded from one to three:
- Grade I: Mild injury with minimally torn fibers and no loss of MCL integrity.
- Grade I: Moderate injury with an incomplete tear and increased laxity of the MCL.
- Grade III: Severe injury with a complete tear and gross laxity of the MCL.
How is MCL injury treated?
The management of a medial collateral ligament (MCL) injury is dependent on the grade of injury:
- Grade I injury: Rest, ice, compression, and elevation (RICE) with analgesics or pain relievers (typically NSAIDs) are used mainly. Strength training as tolerated should be incorporated to return to the full exercise regime by six weeks.
- Grade II injury: Analgesics with a knee brace and weight-bearing/strength training as tolerated. Patients should aim to return to the full exercise regime by 10 weeks.
- Grade III injury: Analgesics with a knee brace and crutches, but if there is any associated distal avulsion then surgery is considered. Patients should aim to return to the full exercise regime by 12 weeks.
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DeBerardino TM. Medial Collateral Knee Ligament Injury. Medscape. https://emedicine.medscape.com/article/89890-overview