Fibular Collateral Ligament Injury - Causes, Symptoms, Diagnosis, and Treatment

Introduction

One of the ligaments located inside the knee is called the lateral collateral ligament (LCL). The LCL connects the femur, or thigh bone, to the tiny bone (fibula) in the lower leg and is located on the outside of the knee joint. A partial or complete tear, as well as a stretched ligament, can result in an LCL injury. The LCL is also referred to as the fibular collateral ligament. The LCL helps stabilize the knee together with the other ligaments in the knee. The medial collateral ligament (MCL) and LCL are responsible for limiting the knee's sideways movement. A sprain occurs when a knee ligament is strained but not ruptured. Depending on how severe they are, sprains are graded in different ways. If the LCL injury is serious, it might also be accompanied by ligament and tendon damage to the knee.

What Are the Causes of Fibular Collateral Ligament Injury?

The most common way for the knee to sustain lateral collateral ligament (LCL) or fibular collateral ligament damage is by being forced outward (away from the other knee). If a person receives a blow to the inside of the leg, as can happen in contact sports like football, this could occur. By turning the foot sideways or stretching the knee above its normal range of motion, one might also harm the LCL. In the event of a severe accident, both the LCL and other knee ligaments may be damaged. An automobile accident or a fall from a height are two examples.

What Are the Symptoms of a Fibular Collateral Ligament Injury?

The following are some signs of a lateral collateral ligament tear:

• Knee enlargement.

• Catching or locking the knee while moving.

• Knee pain or discomfort on the outside.

• A knee that gives way or feels like it will give way when it is active or under certain kinds of stress.

How Is Fibular Collateral Ligament Injury Classified?

According to their severity, LCL injuries are divided into three categories.

• Grade 1 (Mild Sprain) - Localized lateral knee discomfort indicative of the diagnosis. There are no mechanical or instabilities signs.

• Grade 2 (Partial Tear) - Severe localized lateral and posterolateral knee pain, edema (swelling), and diagnosis of partial tear. Although the ligament has a defined termination, there may be 5 to 10 mm of laxity evident.

• Grade 3 (Complete Tear) - Patients' levels of pain and edema vary. It frequently occurs in conjunction with PLC (posterolateral corner) and other related ailments. There is a laxity of greater than 10 mm, and mechanical symptoms are present.

How Is Fibular Collateral Ligament Injury Diagnosed?

• History: Patients typically have a history of an acute incident resembling an excessive noncontact varus bend or a medial blow to the knee while it is completely extended. After the injury, they would complain of quick-onset lateral knee discomfort, swelling, and ecchymosis (bruise). The patient may also describe a thrust gait, in which they complain of their foot thrusting out in the middle of their stance. Patients may also experience weakness or a foot drop in addition to paresthesia (loss of sensation) over the lateral lower extremity.

It is crucial to obtain a thorough history of these patients, taking into account everything from bleeding or clot diseases to past surgeries, occupation, gait, ambulation-assisted devices, and living arrangements (stairs at home).

• Physical Examination: Every patient has to have a thorough knee assessment that includes the full range of motion. The most frequent exam finding, which can also be felt at Gerdy's tubercle, the infrapatellar bursa (sac present below the kneecap), and the patellar tendon attachment, is lateral knee discomfort to palpation. There could be ecchymosis, swelling, and warmth. The standard "varus thrust" finding should be looked for while examining gait.

• Special Tests:

1. The Varus Stress Test: It is the most effective test for determining LCL injury, according to studies. The test is conducted as the examiner's hand stabilizes the femur (thigh bone) and applies a varus force to the ankle while watching the lateral joint line. At first, the test is conducted at 30 degrees. Any lateral compartment gap is a sign of probable PLC and LCL damage. The test is then performed with the knee fully extended. An isolated LCL injury is present if there is enhanced stability when measured in full extension. The test is considered positive for LCL and PLC injuries if instability is still present after being fully extended.

2. External Rotation Recurvatum Test: This test evaluates the posterolateral rotatory stability of the knee. In a supine position, the patient is lying down. The examiner lifts the big toe off the table, externally rotates the tibia with one hand, and applies a downward push through the suprapatellar region. A positive examination is demonstrated by excessive hyperextension in comparison to the unharmed knee. It is significant to note that while this exam is more accurate at diagnosing related ACL injuries, it is less than ten percent accurate at detecting PLC injuries.

3. Posterolateral Drawer Test: The patient lies prone with the knee flexed to 90 degrees and externally rotated 15 degrees, similar to the posterior drawer test. The examiner applies a posterior force while holding the femoral condyles. A PLC injury is suggested by any excessive posterolateral translation of the affected leg.

4. Reverse Pivot Shift: The posterolateral drawer test and this test are both carried out in the same position. The examiner steadily extends the knee while delivering a valgus and external rotational force while keeping an eye on the lateral joint line. The lateral tibial plateau, which was previously sub-luxated (dislocated) and was visible at 90 degrees, is reduced as the ITB (iliotibial band syndrome) changes from a flexion vector to an extension vector at 30 degrees. If there is a discernible "clank" at 30 degrees, the test is considered successful. Due to the possibility of false positives resulting in a significant number of non-injured knees, it is crucial to compare data bilaterally.

5. Dial Test: This exam, which assesses the femur's external rotation, helps determine a PLC injury. The patient is lying face down. The examiner places one hand to support the thigh and rotates the ankle and leg externally with the other. Bilaterally, this test is carried out with the knee flexed at 30 and 90 degrees. A PLC injury is proven by ten degrees or greater of external rotation on the affected leg.

• Imaging Tests:

1. Plain Radiograph - Simple AP and lateral knee radiographs will not show any LCL alterations, but it is crucial to get X-rays to rule out any associated structural issues. There is also a need for varus and kneeling posterior stress radiography. Both have proven to be capable of differentiating between the severity of LCL and PLC injuries, but they also both have a high degree of user reliability.

2. MRI (Magnetic Resonance Imaging) - The gold standard for identifying structural LCL and PLC injuries is MRI. The highest sensitivity and specificity for LCL injury are found in coronal and sagittal T1 and T2 weighted series (around 90 percent). The need for surgery cannot be determined by an MRI alone. A thorough physical examination and radiographs are necessary.

3. Musculoskeletal Ultrasound - When available, musculoskeletal ultrasonography might be a helpful tool in the quick identification of LCL injuries. The LCL will seem thicker and hypoechoic on imaging. The absence of LCL fiber continuity, edema, or dynamic laxity may be visible in a complete tear.

How Is Fibular Collateral Ligament Injury Treated?

Most LCL injuries are manageable with at-home care using:

• Rest and knee protection.

• A cold bag of ice.

• Applying an elastic bandage on the knee (compression).

• Raising (supporting) the knee.

• Inflammatory drug treatment.

To reduce the amount of weight patients exert on their legs, the physician could advise using crutches. Additionally, the doctor could advise putting on a brace that supports and shields the knee while still allowing patients some range of motion.

It could be necessary for patients to slow down temporarily. However, following the doctor's recommendations for mild stretches and range-of-motion exercises will aid in the recovery process.

An extensive tear might require surgery. But unless there is additional harm to the meniscus or anterior cruciate ligament (ACL) in the knee, this is typically not done. Whether additional knee parts are affected, and the severity of the injury will determine how it will be treated.

• Grade 1 or Mild - These wounds could simply require short-term use of crutches and home care. When the physician gives one the all-clear to put weight on the leg, one might also need to wear a hinged knee brace. A lot of people can resume their normal activities after three to four weeks.

• Grade 2 or Moderate - These wounds might need the use of crutches and a hinged knee brace. A lot of individuals can resume their normal activities after eight to 12 weeks.

• Grade 3 or Severe - For at least six weeks, one should avoid putting any weight on the injured leg, and patients might need to wear a hinged brace for a few months. Occasionally, surgery may be required. A lot of people can resume their normal activities after eight to 12 weeks.

Conclusion

The LCL stabilizes the joint and runs along the outside of the knee. The ligament may sustain variable degrees of damage from impacts or abrupt twists during sports or from other types of trauma. Depending on the type of injury and all of the implicated structures, treatment and recovery timeframes will differ significantly. Minor wounds might not have an adverse long-term effect. After an injury, working with a physical therapist may assist in quickly restoring the range of motion by strengthening the injured area.