Medial Collateral and Lateral Collateral Ligament Injury

Updated: May 14, 2019
Author: Adam B Agranoff, MD; Chief Editor: Ryan O Stephenson, DO 



Medial collateral ligament (MCL) and lateral collateral ligament (LCL) injuries of the knee are common. In fact, injury to the MCL is the most common ligamentous knee injury.

The MCL and LCL provide restraint to valgus and varus angulation of the knee, respectively. The MCL has superficial and deep components. The superficial MCL fibers attach proximally to the medial femoral epicondyle and distally to the medial aspect of the tibia, approximately 4 cm distal to the joint line. The deep MCL fibers originate from the medial joint capsule and are attached to the medial meniscus.

The LCL is part of a complex of ligaments collectively named the posterolateral corner (PC). The structures in the PC include the LCL, the popliteofibular ligament, the popliteus ligament, the arcuate ligament, the short lateral ligament, and the posterolateral joint capsule. The LCL is separated from the lateral meniscus by a fat pad (see image below).[1, 2, 3, 4]

The medial and lateral collateral ligaments of the The medial and lateral collateral ligaments of the knee. Courtesy of Randale Sechrest, MD, CEO, Medical Multimedia Group.

Related Medscape Drugs & Diseases topics:

Collateral Ligament Pathology, Knee

Knee, Collateral Ligament Injuries (MRI)

Lateral Collateral Knee Ligament Injury

Medial Collateral Knee Ligament Injury

Related Medscape topic:

Resource Center Joint Disorders


Medial collateral ligament (MCL) and lateral collateral ligament (LCL) injuries are caused primarily by valgus and varus stress (respectively) to the knee joint. Injuries also can occur to both ligaments with excessive lateral rotation of the knee.



United States

The annual incidence of acute knee injury in the United States is estimated to be 300 cases per 100,000 population. Collateral ligament injuries account for 25% of patients presenting to emergency rooms with acute knee injury. Peak incidence of collateral ligament injuries occurs in adults aged 20-34 years. The National Collegiate Athletic Association (NCAA) injury surveillance system reported 2.1 medial or lateral collateral injuries per 1000 player exposures in games across all NCAA sports over 1 year.[5] Even noncontact sports, such as gymnastics and swimming, can lead to collateral ligament injuries.[6]


In a prospective study of Elite Club players in the Union of European Football Associations (UEFA), Lundblad et al found that medial collateral ligament (MCL) injuries accounted for 130 of 4364 registered injuries (3%) occurring among 51 teams over 1-3 full seasons. Ninety-eight MCL injuries (75%) were contact related, with tackling or being tackled representing the most frequent playing-associated contact mechanisms (12% and 29%, respectively).[7]


Medial collateral ligament (MCL) and lateral collateral ligament (LCL) injuries can in most individuals be treated successfully with conservative methods. Severe injuries may require surgical intervention and tend to have good outcomes.[2, 8]


There is no known racial predilection for medial collateral ligament (MCL) and lateral collateral ligament (LCL) injuries.


Unlike anterior cruciate ligament (ACL) injuries, which occur at a higher rate in women, medial collateral ligament (MCL) and lateral collateral ligament (LCL) injuries occur at equal rates in men and women.[6, 9]

Related Medscape Drugs & Diseases articles:

Anterior Cruciate Ligament Pathology

Anterior Cruciate Ligament Injury [Physical Medicine and Rehabilitation]

Anterior Cruciate Ligament Injury [Sports Medicine]

Knee, Anterior Cruciate Ligament Injuries (MRI)


Age patterns for medial collateral ligament (MCL) and lateral collateral ligament (LCL) injuries are bimodal, with the highest incidence rates found in individuals aged 20-34 years and in persons aged 55-65 years. Nonetheless, MCL and LCL injuries can occur at any age.




Listen to the patient's description of the injury event. The force vector of injury to the knee indicates the most likely site of pathology.[10] For example, a football player who complains of medial knee pain after a valgus stress on the knee is likely to have an injury to the medial collateral ligament (MCL). Have the patient use the uninjured knee to explain precisely what he/she was doing when the incident occurred.

  • MCL injury

    • Patients commonly have had recent excessive valgus force applied to a partially flexed knee (eg, a clipping injury in football). A common triad of injury (particularly in athletes) when a valgus force is applied to the knee involves injury to the MCL, the medial meniscus, and the anterior cruciate ligament.

    • Most patients are able to continue ambulating after an acute injury.

    • Pain and stiffness are localized to the medial knee.

    • Erythema may appear after several days.

    • The location of pain and swelling can be good indicators of which structure(s) may be damaged in the knee.

    • Instability or mechanical symptoms (eg, a locking or popping sensation) are uncommon.

  • Lateral collateral ligament (LCL) injury

    • The patient commonly reports a history of varus force applied to the knee.

    • Most patients are able to continue ambulating after an acute injury.

    • Pain and stiffness are localized to the lateral knee.

    • Erythema may appear after several days.

    • Swelling is often present.

    • Instability or mechanical symptoms (eg, a locking or popping sensation) are uncommon.


Recognize that collateral ligament injuries often are seen in association with injury to other knee structures. A comprehensive musculoskeletal knee examination should be completed to direct further diagnostic testing and therapeutic interventions. A systematic review of the available literature revealed no articles that adequately assessed the diagnostic sensitivity and specificity of a physical examination in detecting medial and lateral collateral ligamentous injuries.

  • Medial collateral ligament (MCL) injury

    • Palpate with the knee in 25-30 º of flexion.

    • Tenderness may be noted anywhere along the course of the MCL.

    • Isolated tenderness at the proximal or distal insertion sites may indicate an avulsion-type injury.

    • Swelling often is present and should alert the examiner to possible intra-articular injury.

  • Lateral collateral ligament (LCL) injury

    • Palpate with the knee in 20 º of flexion.

    • Tenderness may be noted anywhere along the course of the LCL.

    • Isolated tenderness at the proximal or distal insertion sites may indicate an avulsion-type injury.

    • Swelling is common.

  • Evocative testing of collateral ligaments

    • Valgus stress testing of the MCL

      • The patient is in the supine position with the knee flexed 25-30 º. The examiner places one hand on the lateral knee and grasps the medial ankle with the other hand. Then the knee is abducted. Pain and excessive laxity indicate stretching or tearing of the MCL.

      • Perform the same technique as above with the knee extended. If excessive knee joint laxity and pain are still noted, injury to the anterior cruciate ligament also may be present.

    • Varus stress testing of the LCL

      • The patient is in the supine position with the knee flexed 20-25 º. The examiner places one hand on the medial knee and grasps the lateral ankle with other hand. The knee is adducted. Pain and excessive laxity indicate injury to the LCL.

      • Then perform the same technique as above with the knee extended. If pain and laxity are still present, injury to the posterior capsule may be present.

  • Injury severity

    • Grade I - Less than 5 cm laxity (partial tear)

    • Grade II - 5-10 cm laxity

    • Grade III - More than 10 cm laxity (complete tear)

  • Physical examination under general anesthesia may be indicated if the patient is guarding due to pain symptoms.


See the list below:

  • Injury to the medial collateral ligament (MCL) or lateral collateral ligament (LCL) may be caused by the following:

    • Trauma

      • Acute varus or valgus stress on the knee joint

      • Sports related (younger population)

      • Falls (elderly)

      • Other trauma

    • Overuse syndromes (for example, swimmers who use the breaststroke may repetitively stretch the MCL, leading to injury)

A study by Lee et al reported that in children and adolescents with anterior cruciate ligament (ACL) tears, older age and contact injuries are risk factors for concomitant lateral and medial collateral ligament injuries. The study also found the proportion of chondral injuries in patients with concomitant collateral ligament trauma to be higher than in the rest of the group.[11]  



Diagnostic Considerations

These include the following:

  • Osteochondral fracture

  • Extensor mechanism rupture

  • Osteonecrosis of the femoral epicondyle

  • Osteonecrosis of the tibial condyle

  • Inflammatory conditions (systemic disease)

Differential Diagnoses



Laboratory Studies

See the list below:

  • Laboratory studies usually are not indicated for the diagnosis of a medial collateral ligament (MCL) or lateral collateral ligament (LCL) injury.

Imaging Studies

See the list below:

  • Diagnosis of a medial collateral ligament (MCL) or lateral collateral ligament (LCL) injury is usually clinical.[8, 12, 13]

  • Plain films in patients with suspected knee ligamentous injuries should include anteroposterior, lateral, intercondylar notch, and sunrise views. Avulsion fractures are often noted in knee ligament injuries. Indications for plain knee radiographs in suspected knee ligamentous injuries (Pittsburgh decision rules) are blunt trauma or a fall with one of the following criterion:

    • The patient is unable to walk 4 weight-bearing steps.

    • The patient is older than 50 years or younger than 12 years.

  • Magnetic resonance imaging (MRI) is helpful for ruling out other soft-tissue injuries (eg, anterior or posterior cruciate ligament tears, meniscus injury). MRI is very sensitive in detecting tears of the collateral ligaments. However, it is not reliable for differentiating grades of injury, and use of the modality can lead to underestimation of the degree of injury.[14, 15]

    • The MCL can usually be visualized in its entirety in the coronal plane. A partial tear of the MCL is seen on T2-weighted MRI scans as an area of increased signal intensity, representing edema. The ligament may irregular. A complete tear of the MCL is marked by edema at the rupture site and retraction of the free ends.

    • The LCL is best visualized on coronal images. It tends to be of low signal intensity and have uniform thickness. Partial tears are characterized by edema. A complete LCL tear may be associated with a small avulsion of the styloid process of the fibular head and with marked edema.


See the list below:

  • If an effusion is present, arthrocentesis of the knee may be indicated to rule out hemarthrosis.



Rehabilitation Program

Physical Therapy

The type of physical therapy (PT) treatment indicated for a medial collateral ligament (MCL) injury depends on the severity of the injury.[8, 16] Recommendations for treatment include the following:

  • Grade I - Compression, elevation, and cryotherapy are recommended. Short-term use of crutches may be indicated, with weight-bearing–as–tolerated (WBAT) ambulation. Early ambulation is recommended.

  • Grade II - A short-hinged brace that blocks 20º of terminal extension but allows full flexion should be used. The patient may ambulate, WBAT. Closed-chain exercises allow for strengthening of knee musculature without putting stress on the ligaments.

  • Grade III - The patient initially should be non–weight-bearing (NWB) on the affected lower extremity. A hinged braced should be used, with gradual progression to full weight-bearing (FWB) over 4 weeks. Grade III injuries may require 8-12 weeks to heal.

All MCL injuries should be treated with early range of motion (ROM) and strengthening of musculature that stabilizes the knee joint. Conservative measures usually are adequate, but, if the patient fails to progress with treatment, a meniscal or cruciate ligament tear is suggested.

Lateral collateral ligament (LCL) injuries heal more slowly than do MCL injuries, due to the difference in collagen density. Recommendations for the treatment of LCL injuries include the following:

  • Grades I and II - These injuries are treated according to a regimen similar to that for MCL injuries of the same severity. A hinged brace is used for 4-6 weeks.

  • Grade III - Severe LCL injuries typically are treated surgically due to rotational instability, because they usually involve the posterolateral corner of the knee. Patients may require bracing and physical therapy for up to 3 months in order to prevent later instability.

Surgical Intervention

Most patients with a collateral ligament injury can be treated effectively with conservative measures. Grade III lateral collateral ligament (LCL) tears usually involve the posterolateral complex and are associated with instability. These patients do require surgical repair.[17, 18, 19, 20, 21] Surgical treatment for isolated injuries of the medial collateral ligament (MCL) or LCL is a controversial topic. The treatment plan should be based partially on the patient's pre-injury level of activity and on motivational factors. For example, a young competitive swimmer may want surgery, followed by a comprehensive rehabilitation program to accelerate the time needed for adequate functional recovery.[22] A technique for repairing severe MCL injuries using autogenous hamstring tendons has been proposed.[23]

A study by Dong et al indicated that both anatomic ligament repair and triangular ligament reconstruction are about equally effective in the treatment of acute grade III MCL tear combined with anterior cruciate ligament (ACL) tear. The study, which involved 64 patients, had a mean 34-month follow-up period. Although International Knee Documentation Committee (IKDC) scores and evaluation of the medial opening of the knee showed no significant differences between the techniques, the investigators did find that patients who underwent triangular ligament reconstruction had a significantly lower incidence of anteromedial rotatory instability than did the anatomic ligament repair patients at final follow-up.[24]

A retrospective study by King et al looking at multiligament repair/reconstruction for medial (ACL, posterior cruciate ligament [PCL], MCL) and lateral (ACL, PCL, LCL) knee dislocations indicated that compared with medial repair, medial reconstruction and lateral repair/reconstruction are more likely to produce positive results; medial repair was associated with worse Lysholm Knee and IKDC scores.[25]


An orthopedic surgery consultation is advised for individuals with severe ligament injury.



Medication Summary

The goal of pharmacotherapy is to reduce morbidity.

Nonsteroidal anti-inflammatory drugs

Class Summary

These have analgesic, anti-inflammatory, and antipyretic activity. Their mechanism of action is not known, but they may inhibit cyclo-oxygenase activity and prostaglandin synthesis. Other mechanisms may exist as well, such as inhibition of leukotriene synthesis, lysosomal enzyme release, lipoxygenase activity, neutrophil aggregation, and various cell-membrane functions.

Ibuprofen (Motrin, Ibuprin)

DOC for patients with mild to moderate pain. Inhibits inflammatory reactions and pain by decreasing prostaglandin synthesis.

Celecoxib (Celebrex)

Primarily inhibits COX-2. COX-2 is considered an inducible iso-enzyme; it is induced by pain and inflammatory stimuli. Inhibition of COX-1 may contribute to NSAID GI toxicity. At therapeutic concentrations, COX-1 iso-enzyme is not inhibited; thus, incidence of GI toxicity, such as endoscopic peptic ulcers, bleeding ulcers, perforations, and obstructions, may be decreased when compared with nonselective NSAIDs. Seek lowest dose for each patient.

Neutralizes circulating myelin antibodies through anti-idiotypic antibodies; down-regulates pro-inflammatory cytokines, including INF-gamma; blocks Fc receptors on macrophages; suppresses inducer T and B cells and augments suppressor T cells; blocks complement cascade; promotes remyelination; may increase CSF IgG (10%).

Has a sulfonamide chain and is primarily dependent on cytochrome P450 enzymes (a hepatic enzyme) for metabolism.

Analgesics, miscellaneous

Class Summary

Pain control is essential to quality patient care. Analgesics ensure patient comfort, promote pulmonary toilet, and have sedating properties, which are beneficial for patients who have sustained trauma or injuries.

Tramadol (Ultram)

Inhibits ascending pain pathways by binding to mu-opiate receptors in CNS, thus altering perception of and response to pain. Also inhibits re-uptake of norepinephrine and serotonin.



Further Outpatient Care

Patients who undergo surgery for grade III lateral collateral ligament (LCL) injuries are later referred to outpatient PT for rehabilitation. The process of recovery and rehabilitation may take up to 3 months. Less severe injuries of the medial collateral ligament (MCL) and LCL also are commonly referred for outpatient PT treatment (see Physical Therapy).[16]

Further Inpatient Care

Depending on each individual case and on the complexity of a lateral collateral ligament (LCL) injury that requires surgery, patients may or may not need inpatient care. If the patient requires hospitalization, education should be completed prior to dismissal. Physical therapy may be ordered to complete crutch and stair training, thus ensuring the patient's safety upon his/her return home.


Peroneal nerve injuries can occur with lateral collateral ligament (LCL) injuries.

A Swedish study, by Svantesson et al, of 19,457 patients over age 15 years who underwent primary anterior cruciate ligament (ACL) reconstruction reported that in such cases, the risk for ACL revision may be greater in those who receive conservative, rather than surgical, treatment for a concomitant medial collateral ligament (MCL) injury. Nonetheless, the investigators found that patients tended to report worse knee function at 2-year follow-up for surgical treatment of MCL trauma.[26]


Most patients have an excellent outcome.[8]

Patient Education

Depending on their age and activity level, patients may need education and training in the use of the most appropriate assistive device (eg, crutches, walker). Education is important throughout the patient's recovery. Proper treatment strategies and a home exercise program to increase knee joint stability further and avoid recurrence are essential elements of patient education.

For patient education resources, see the Foot, Ankle, Knee, and Hip Center, as well as Knee Injury and Knee Pain.