Ligaments are the band of connective tissues that join two separate bones. The collateral ligaments are the connective tissues that joins the shin bone to the tibia and the fibula. These ligaments control the lateral motion of the knee and protect the joint against any untoward movement. The collateral ligaments are of two types:
The medial collateral ligament (MCL) runs on the inside and connects the femur to the tibia.
The lateral collateral ligament (LCL) runs on the outside, connecting the femur to the fibula.
There is another set of ligaments found inside the knee joint, which controls the front and back motion of the knee. These are the cruciate ligaments which are of two types: the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL), which cross each other, forming an X.
Who Is Susceptible to Collateral Ligament Pathology?
Medial collateral ligament injuries are the most common type of ligamentous injury of the knee, which accounts for almost 40 percent of all knee injuries.
The lateral collateral ligament rarely occurs in isolation and is often accompanied by ACL or PCL injuries. Isolated LCL injuries have an incidence of just 7.9 percent in high school athletes. LCL injury, in combination with PCL injury, occurs in 40 percent of injuries caused due to contact sports.
What Is the Anatomy of Collateral Ligaments?
The medial collateral ligament has two parts: superficial and deep. The superficial part originates from the medial femoral epicondyle; the proximal division inserts into the semimembranosus tendon, and the distal division inserts into the posteromedial crest of the tibia.
The deep MCL is divided into the meniscofemoral and meniscotibial ligaments. The meniscofemoral segment originates from the femur just distal to the superficial medial collateral, inserting into the medial menisci, and the meniscotibial ligament originates from the medial meniscus and inserts into the distal edge of the articular cartilage of the medial tibial plateau.
Blood supply to the MCL is from the branches of the superior and inferior genicular arterial supply. Nerve innervation is by the medial articular nerve which is a branch of the saphenous nerve.
The MCL is the primary static stabilizer of the knee, assisting in the passive stabilization of the joint. It is the primary responder to Vegas stress and a secondary resistor against the rotational forces. The MCL guides the knee joint through a full range of motion under tensile load, prevents hyperextension of the joint and posterior translation of the tibia, and evokes neurological feedback during excess stretching or loading.
The lateral collateral ligament is a cord-like band originating from the lateral epicondyle of the femur and inserted into the fibula head. Blood supply arises from the popliteal artery, which are the branches of the superior and inferior genicular arteries. The nerve innervation is by the common fibular nerve. The LCL is the primary resistor of varus stress in knee flexion, provides posterolateral stability to the knee, and prevents medial translation of the tibia. The LCL also plays a minor role in stabilizing anterior and posterior tibial translation in case of ACL tears.
What Causes Collateral Ligament Pathology?
MCL injuries are caused by abrupt turning, cutting, twisting, or direct trauma to the lateral knee, creating excessive valgus stress. MCL injuries frequently occur in an 'unhappy triad' involving injuries to the MCL, ACL, and medial meniscus.
LCL injuries are caused due to high-intensity trauma to the anteromedial knee that causes hyperextension and creates extreme varus force. Non-contact hyperextension and varus stressors have also been etiological to LCL injuries.
What Are the Types of Collateral Ligament Pathologies?
MCL injuries are graded on the basis of a valgus stress test where the joint is brought into flexion by the examiner.
Grade 1: Tenderness along the MCL under valgus stress but with little to no joint opening.
Grade 2: Some joint opening with a firm endpoint.
Grade 3: Significant joint opening with no endpoint.
MCL injuries are also classified on the basis of the severity of the injury, as concluded from MRI reports.
Type I: Pre-avulsion injury.
Type II: Avulsion injury.
Type III: Midsubstance tear of MCL in a zigzag pattern.
Type IV: Distal MCL detachment, shredded and hanging.
Type V: Proximal sleeve detachment of MCL and capsule with a buttonhole of the medial femoral condyle.
LCL injuries are graded according to the severity of the ligament tear.
Grade 1: Mild sprain.
Grade 2: Partial tear.
Grade 3: Complete tear.
What Are the Symptoms of Collateral Ligament Pathologies?
The symptoms of MCL injuries include a sudden onset of pain or swelling after a sporting or traumatic event with a pop sound heard during the incident. The patient may or may not complain of knee instability and inability to walk. The injury may be accompanied by joint effusion, ecchymosis (bleeding under the skin), tenderness at the site of ligament attachment, and antalgic or vaulting gait (types of altered gait).
The patient with LCL injury complains of sudden onset of lateral knee pain, warmth, swelling, and ecchymosis after an acute event consistent with a medial trauma to the knee. The patient shows a thrusting gait, foot kicking in mid-stance along with paresthesia over the lateral lower extremity, as well as weakness and foot drop.
How to Diagnose Collateral Ligament Pathologies?
The patient should be evaluated for a history of recent traumatic injury to the knee. A physical examination, along with radiographic evidence, is required to diagnose a collateral ligament pathology.
1. Physical Examination:
MCL injury evaluation requires a complete history of trauma along with local inspection and palpation. Localized effusion and tenderness with altered gait can be observed. Palpation reveals tenderness at the site of the detachment of the ligament. A Valgus stress test is conducted to determine the integrity of the ligament.
LCL injuries require a full range of motion, knee exam by the clinician especially focussing on tenderness along the lateral knee, infrapatellar bursa, Gerdy's tubercle, and the patellar tendon attachment. Special tests like the varus stress test, external rotation recurvatum test, posterolateral drawer test, reverse pivot shift test, and dial test can also be performed to assess the extent and severity of LCL injury.
Apart from these radiographs, MRIs and musculoskeletal ultrasounds can be ordered.
MCL: Evaluation of occult and avulsion fractures and ossification of MCL near its attachment.
LCL: To rule out fibular head fractures or avulsions, tibial spine avulsions, lateral tibial plateau avulsion of the styloid of the proximal fibula, segond fractures, and underlying arthritic changes.
3. MRIs (Magnetic Resonance Imaging):
MCL: Additional information about the soft tissue of the knee and rule out meniscal or capsular tearing.
LCL: MRIs are the gold standard in diagnosing LCL and PCL injuries. Coronal and sagittal T1 and T2 weighted series have the highest sensitivity and specificity for LCL injury.
4. Musculoskeletal Ultrasound:
MCL: Can be used to identify the injury location and severity and offers additional benefits while performing dynamic valgus stress tests.
LCL: Rapid diagnosis of LCL injury. The image will show a thick and hypoechoic ligament with edema, dynamic laxity, or lack of fiber continuity (in the case of grade 3 tears).
What Is the Differential Diagnosis of Collateral Ligament Pathologies?
Differential Diagnosis of MCL:
Crystal-induced inflammatory arthropathy.
Osteoarthritis (arthritis due to joint cartilage degeneration).
Overuse syndromes (due to repetitive usage).
Patellar subluxation (sliding out of the kneecap).
Patellar tendonitis (inflammation of the patellar tendon).
Popliteal cyst (a growth or cyst behind the knee).
Slipped capital femoral epiphysis (damaged growth plate and slip of the head of the femur bone).
Tibial apophysitis (repeated strain and microtrauma cause pain below the knee cap).
Differential Diagnosis of LCL:
ACL/PCL tears (tears of the ACL or PCL ligaments).
Lateral meniscus tear (tear of one of the bands of knee cartilage).
Popliteal injury (tear or strain of the popliteal muscle).
Bone contusion (bone bruise).
IT band syndrome (swelling or irritation of the iliotibial band of tendons).
How to Treat or Manage Collateral Ligament Pathologies?
1. Management of MCL Injuries:
Grade I and II MCL injuries are often treated with a conservative approach unless a serious underlying injury is caused, as it has shown over 98 percent effectiveness in athletes. NSAIDs are prescribed against pain and inflammation. Knee mobilizers and clutches are advised for short-term injuries, followed by gradual weaning of medications and physical therapy. Grade I injuries have end of treatment and back to action within 10 to 14 days. Grade II injuries have a more variable recovery timeline till equal strength in both legs is achieved.
Grade III MCL injuries are treated with a conservative or operative approach. Operational therapy is mostly preferred as these tears can lead to rotational instability. Grade III tears are often associated with other injuries like ACL tears which are repaired with allograft and autograft. Post-surgery, a hinged brace is locked at 30° (degree) flexion with touch weight bearing for three weeks, and physical therapies up to 90 motion can be performed. Thereafter the complete range of motion is unlocked, and the patient can proceed with closed kinetic chain exercises and higher resistance strength exercises.
2. Management of LCL Injuries:
All grades of LCL can be treated with rest, compression, NSAIDs (non-steroidal anti-inflammatory drugs), and an ice pack. The ice pack should not be used for more than 15 minutes to prevent cold injury to the common peroneal nerve.
Grades 1 and 2 are therapeutically managed with one week of non-weight bearing and clutches for better pain control. During three to six weeks, hinged knee braces are used to stabilize the medial and lateral aspects of the joint with functional rehabilitation.
In isolated LCL grade 3 injuries, both ranges of motion improvement and pain reduction were achieved through surgical management. Reconstruction surgeries using semitendinosus autografts have been the most successful in treating LCL grade 3 injuries. Preservation of the common peroneal nerve and ACL must be taken care of to avoid any complications.
What Is the Prognosis of Collateral Ligament Pathologies?
Collateral ligament anthologies have a good prognosis when they are managed efficiently. Grades 1 and 2 of both MCL and LCL have been proven to show great effectiveness with non-surgical therapeutic treatment followed by physical therapy. While grade 3 injuries require surgical intervention, they require substantial post-surgical physical therapy. All kinds of collateral ligament injuries often heal with a good prognosis.
An interdepartmental approach toward ligament injuries is required to facilitate quick recovery. An emergency physician, orthopedic surgeon, and physical therapist are to be included in the treatment regimen. The initial protocol consists of RICE (rest, ice, compression, and elevation), followed by diagnostic modalities, including MRIs, and finally, surgical intervention (if indicated). Even though the recovery has shown a good prognosis, some grade 3 injuries have shown longer recovery periods of over four months, during which physical therapy becomes of utmost importance.