Lateral Collateral Knee Ligament Injury
Lateral collateral ligament (LCL) injuries occur from a varus force to the knee (ie, a force directed at the medial side of the knee or leg). These injuries are much less common than medial collateral ligament (MCL) injuries because the opposite leg usually guards against direct blows to the medial side of the knee. However, LCL injuries can occur in situations in which trauma occurs as the leg is extended in front of the body, such as when attempting to gain control of the ball from another player in soccer or rugby (eg, tackling). (See also the eMedicine article Medial Collateral and Lateral Collateral Ligament Injury.)
The LCL is a round ligament that lies beneath the tendon of the biceps femoris muscle and runs from the lateral epicondyle, anterior to the origin of the gastrocnemius muscle, to the fibular head. The LCL lies just posterior to mid-axial point of the knee and is the primary restraint to varus stress in the knee.
The LCL is taut when the knee is extended, and it is loose when flexed more than 30°.1 Unlike the MCL, the LCL is not attached to the lateral meniscus but is separated from it by a small fat pad. The LCL is the primary restraint to varus rotation (coronal plane force) from 0-30° of knee flexion and secondarily resists internal rotation of the tibia.
The mechanism of injury is the most important component of the patient history to determine the possible injured structures. Direct contact to the anteromedial aspect of the tibia is the most likely cause of injury to the LCL.
Ascertain whether the patient noted any effusion within a few hours following the incident. One should not expect a significant joint effusion unless there also is a cruciate ligament or meniscal tear. It is also important to determine whether the individual felt or heard a pop in the knee, as this may suggest a concomitant injury. (See also the eMedicine articles Posterior Cruciate Ligament Injury, and Meniscus Injuries)
Inquire about previous knee symptoms, injuries, or surgeries.
Discuss and obtain the patient’s age, occupation, recreational activities, lifestyle, and interests to help determine the proper course of treatment.
A more concerning injury is one that involves the posterior lateral complex. The most important structures in this complex include the iliotibial tract, long and short head of the biceps femoris muscle, fibular collateral ligament, posterior arcuate ligaments, and the posterior capsule. The peroneal nerve can also be injured because of its proximity to the biceps tendon; this type of injury requires extensive surgical repair because of the complex structures involved. The surgery should be individualized to each patient and his or her specific injuries. (See also the eMedicine article Iliotibial Band Syndrome.)
Examine the injured extremity.
Inspect the leg for gross abnormalities, skin abrasions, and other signs.
Inspect and palpate the suprapatellar pouch for effusion.
Palpate for joint-line tenderness.
Perform special tests for LCL stability: Varus stress occurs at 0° and 30° of flexion. The LCL is isolated at 30°; testing at 0° also evaluates the posterolateral corner structures and cruciate ligaments.
Physical examination clues of posterolateral injury include footdrop, peroneal nerve injury, tenderness in the posterolateral corner, and pain with posterior-internal rotation of the tibia. (See also the eMedicine article Foot Drop.)
Assess the cruciate ligaments and the menisci.
Evaluate for effusion.
Examine the uninvolved extremity. Compare the alignment, motion, swelling, and ligamentous stability of the affected limb with the injured extremity.
Grade the degree of the LCL injury according to the following2, 3:
Grade 1 – Interstitial injury without laxity is present, but there is pain with varus stress; only microscopic tearing has occurred.
Grade 2 – A 5-10 mm of joint-space opening with a distinct end point is noted; partial macroscopic tearing has occurred.
Grade 3 – Complete tearing (>10 mm joint-space opening) has occurred; complete macroscopic tearing is noted.
LCL injury is caused by a direct blow to the medial aspect of the knee or the anterior medial tibia with the foot planted and the knee in various degrees of flexion.
An LCL injury should not be confused with other overuse lateral knee injuries