Medial Collateral Knee Ligament Injury

Updated: Oct 27, 2022
Author: Thomas M DeBerardino, MD, FAAOS, FAOA; Chief Editor: Craig C Young, MD 


Practice Essentials

Medial collateral ligament (MCL) injuries of the knee are very common sports-related injuries. The MCL is the most commonly injured knee ligament. Injuries to the MCL occur in almost all sports and in all age groups.

Contact sports such as hockey, wrestling, rugby, football, and judo are responsible for the most MCL injuries. Intercollegiate athletes (males more than females) are most at risk for MCL sprain in an intercollegiate cohort, with an average of just over 3 weeks of time lost due to mild sprains as recently reported by Roach et al.[1]

Contact, noncontact, and overuse mechanisms are involved in causing MCL injuries.

  • Contact injuries involve a direct valgus load to the knee. This is the usual mechanism in a complete tear.

  • Noncontact, or indirect, injuries are observed with deceleration, cutting, and pivoting motions. These mechanisms tend to cause partial tears.

  • Overuse injuries of the MCL have been described in swimmers. The whip-kick technique of the breaststroke has been implicated. This technique involves repetitive valgus loads across the knee.

For patient education resources from eMedicineHealth, see Knee Injury and Knee Pain.


United States statistics

The incidence of MCL injuries is impossible to determine because of the wide spectrum of injury severity. Many MCL injuries are minor and may never be evaluated by a physician.[2]

International statistics

In a study of players in the Union of European Football Associations (UEFA), Lundblad et al reported that MCL injuries accounted for 130 of 4364 registered injuries (3%) that occurred among 51 teams during 1-3 full seasons. Ninety-eight MCL injuries (75%) were contact related; tackling or being tackled represented the most frequent playing-associated contact mechanisms (12% and 29%, respectively).[3]

Functional Anatomy

The medial aspect of the knee has been divided into 3 distinct layers based on cadaver dissection. The first layer is the deep fascia, which consists of the sartorius fascia anteriorly and a thin fascial layer posteriorly. The thin posterior fascia covers the popliteal fossa and the heads of the gastrocnemius muscle. The second layer includes the superficial MCL, also known as the tibial collateral ligament. This ligament attaches proximally to the medial femoral epicondyle and to the tibia distally, approximately 4-5 cm distal to the joint line. The parapatellar retinaculum and patellofemoral ligament are within this layer.

The third layer is the knee joint capsule, which attaches proximally and distally at the articular margins. The capsule is divided into thirds from anterior to posterior. The anterior third of the capsule is the thinnest portion. It is attached to the anterior horn of the medial meniscus and is reinforced by the medial retinaculum. The middle third of the capsule consists of the deep medial collateral ligament. It is firmly attached to the mid body of the medial meniscus. Proximal to the meniscal attachment, it is termed the meniscofemoral ligament. Distal to its meniscal attachment, it is termed the meniscotibial ligament. The posterior third of the capsule includes the posterior oblique ligament (POL) and the oblique popliteal ligament. The POL has 3 arms, the superficial, tibial, and capsular.

See the figure below.

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

Sport Specific Biomechanics

The superficial MCL has been shown through serial cutting studies to provide the primary restraint to valgus loads at all degrees of flexion. It is also an important restraint to anterior tibial translation when the anterior cruciate ligament is injured. The superficial MCL acts as a primary restraint to external rotation of the tibia.

Stability of the medial side of the knee is provided by dynamic and static restraints. The static restraints are the superficial MCL and the joint capsule, including the deep MCL and the POL. The semimembranosus muscle, the pes anserine muscles, and the vastus medialis muscle provide dynamic stability. The muscles of the pes include the sartorius, gracilis, and semitendinosus. These muscles flex and internally rotate the tibia. The semimembranosus has 4 attachments: direct, tibial, inferior, and capsular.[4, 5]


Patients with grade 1 and 2 injuries consistently recover well, and athletes return to play early. Patients with isolated grade 3 injuries also consistently return to full preinjury level, but recovery takes longer.


Late instability can occur, requiring operative intervention.




A thorough history should be obtained prior to performing the physical examination. The following questions should be answered:

  • How and when did the injury occur?

  • What was the mechanism of injury?

  • What was the position of the knee at the time of injury?

  • Was the patient able to ambulate immediately after the injury? If so, is the patient still able to ambulate?

  • Did the knee swell immediately or was swelling delayed?

  • Did the patient experience a sensation of a tearing or hear an audible pop?

  • Did any deformity occur? (Deformity may signify a patella subluxation or dislocation.)

  • Have any prior injuries or fractures occurred?

  • Where is the site of injury within the MCL?

Physical Examination

A complete physical examination of the knee should be performed after a thorough history is obtained. Attention should be directed toward localizing the MCL injury and identifying any associated injuries.

  • Inspection and palpation of the knee should identify the presence and location of point tenderness, localized soft tissue swelling, deformity, or ecchymosis. The region of injury within the ligament should be noted. A large joint effusion indicates an associated intra-articular injury. Outcome can be influenced by the location of the injury within the ligament.

  • The integrity of the MCL is tested with a valgus stress. If any abnormal laxity is noted, the quality of the endpoint should be determined. Testing should be performed in full extension and at 30° of flexion. Grading of the injury is based on the amount of laxity. Any laxity is compared to the opposite knee.

  • Rotation should be compared to the opposite knee when evaluating for associated posteromedial injuries.

  • Anterior and posterior draw signs and a Lachman are performed to rule out associated injuries.

  • Associated injuries include the following:

    • Other structures within the knee may be injured in association with the MCL. The anterior cruciate ligament (ACL) is injured in approximately 20% of grade 1 injuries and as many as 78% of grade 3 injuries.

    • The medial meniscus is injured 5-25% of the time; the incidence increases with severity of the MCL injury.

    • The extensor mechanism, including the vastus medialis obliquus and retinacular fibers, is also injured in 9-21% of the cases.

    • The posterior cruciate ligament (PCL) may be injured, but no incidence has been reported.

  • Classification systems include the following:

    • American Medical Association Committee on the Medical Aspects of Sports (1966)

      • Grade 1 - 0-5 mm of opening

      • Grade 2 - 5-10 mm of opening

      • Grade 3 - Greater than 10 mm of opening

    • O'Donoghue classification

      • Grade 1 - Few torn fibers, structurally intact

      • Grade 2 - Incomplete tear, no pathologic laxity

      • Grade 3 - Complete tear, pathologic laxity



Differential Diagnoses



Imaging Studies


Radiography should be performed to rule out fractures of the tibial plateau, patella, or distal femur. Osteochondral effects can also be observed. Anterior-posterior, lateral, and patellofemoral views are usually sufficient. In skeletally immature patients, stress views may be helpful in identifying an associated physeal injury.[6]

The Pellegrini-Stieda lesion is indicative of an old injury and appears as a calcification at the femoral insertion of the MCL.[6]

The lateral capsular sign, or Segond fracture, suggests an associated ACL tear. This is a chip of bone still attached to the capsule after the capsule is avulsed from the lateral tibia.[6]

Stress radiography is a useful adjunct for confirming the grade of MCL injury. Valgus stress radiographs have been shown to accurately and reliably measure medial compartment opening. Differentiation between either meniscofemoral- and meniscotibial-based injuries was noted to be difficult. When comparing with the normal opposite knee at 20° of flexion, a grade III MCL injury is suspected if greater than 3.2 mm of medial compartment opening is noted. Valgus stress radiographs provide objective and reproducible measurements of medial compartment opening.[7]

Magnetic resonance imaging (MRI)

MRI is indicated when associated injuries are suspected. Associated ACL, PCL, and meniscal tears can be identified. Osteochondral fractures and bone bruises may also be identified. Injury of the MCL can be localized to the femoral, midsubstance, or tibial regions.[2]

A systematic review by Meyer et al showed that the correlation of MRI findings with physical examination findings was moderate to strong (65-92%) in patients with MCL injuries. In addition, MRI was more sensitive than physical examination in identifying MCL lesions.[8]

Diagnostic ultrasonography

Studies have suggested that diagnostic ultrasonography can be useful in evaluating MCL injuries.


Joint aspiration

If a significant joint effusion is present, evaluation may be difficult. Using aseptic technique, the knee may be aspirated to allow for a more complete evaluation. A local anesthetic can be injected if the knee is too painful for evaluation.



Acute Phase

Rehabilitation Program

Physical Therapy

The initial treatment of all sprains is similar and follows the RICE protocol with rest, ice, compression, and elevation. Protective weightbearing is instituted with crutches. This is continued until a normal gait is obtained. The severity of the injury dictates further treatment.

Grade 1 and 2 sprains are routinely treated nonoperatively. They may be braced with a knee sleeve or a double-upright hinged knee orthosis, individualized to the patient's discomfort. Crutches are only necessary for a few days. These injuries represent incomplete tears and allow for a rapid return to activities.

Historically, grade 3 tears were treated operatively but currently are routinely treated nonoperatively. In the past, nonoperative treatment meant a long leg cast. Currently, bracing with a hinged knee orthosis is common. Some authors recommend immediate braced increase in range of motion (ROM), while others prefer waiting up to 6 weeks with the knee at 30° of flexion. Crutches are usually necessary for 1-2 weeks.

The goals of therapy are to decrease pain, restore ROM, and regain strength. Crutches are used until weightbearing is comfortable. ROM exercises are performed in a cold whirlpool. Quadriceps strengthening is started with quad sets and progressed to closed-chain exercises as tolerated. Running is allowed when weightbearing is comfortable and is progressed to more narrow S-shaped patterns, until pivoting is comfortable. At this point, sport-specific exercises and drills are added and advanced until the athlete is ready to return to the sport. Return to play is allowed when sport-specific agility testing is performed comfortably. People with grade 1 and 2 injuries usually return to play within 2-3 weeks. People with grade 3 injuries frequently require 6 or more weeks before a return to play.

After sufficient healing of the ligament has occurred, the initial focus of rehabilitation is to restore full ROM. After acceptable knee ROM is restored, the therapist is to concentrate on controlled strengthening. Often in the knee, the functional strength of the quadriceps muscle, especially the medial VMO muscle, is weak and atrophied. After restoration of sufficient strength, the athlete needs to go through sport-specific or function-based training. Upon achieving full strength and pain-free ROM in the lower extremity, the athlete can be cleared to return to their sport, most often without any brace or external support.

Medical Issues/Complications

Persistent instability and laxity may require surgical treatment.

Surgical Intervention

The consensus is that isolated MCL tears rarely require operative repair, while treatment of severe combined ruptures of the MCL and ACL or PCL would require reconstruction.[9] A study found that nonoperative and operative treatments of medial collateral ligament injuries lead to equally good results. Another indication for surgical intervention would be persistent instability, with surgery consisting of tissue repair and imbrication. Often, reinforcement with an allograft is necessary.

Lind et al investigated the effectiveness of treating chronic valgus instability of the knee with a surgical reconstruction technique involving the MCL and the posteromedial corner of the knee.[10] Patients in the study underwent either isolated MCL reconstruction, combined MCL and ACL reconstruction, or multiple ligament reconstruction, with surgery in each case including the use of ipsilateral semitendinosus autografts for MCL and posteromedial reconstruction. In the 50 patients who received a follow-up examination more than 2 years postsurgery, substantial improvements were seen in the International Knee Documentation Committee (IKDC) scores.

A retrospective study by Pandey et al compared outcomes in 35 patients who were divided into two groups, a group who had primary MCL- posteromedial corner repair without subsequent ACL reconstruction and group who a primary MCL- posteromedial corner repaired with a delayed ACL reconstruction. The study reported that the Lysholm (94.6 vs. 91.06) and IKDC (86.3 vs. 77.6) scores of the group that included the delayed ACL reconstruction were higher and 60% of the patients in the group that did not undergo ACL reconstruction complained of instability vs 0% in the ACL reconstructed group.[11]

Recovery Phase

Rehabilitation Program

Physical Therapy

Long-term outcome studies have shown that almost all patients with grade 1 and 2 injuries have returned to full preinjury activities by 3 months. Isolated grade 3 injuries still allow excellent return to preactivity levels by 6-9 months.

Return to Play

Return to play is allowed when sport-specific agility testing is completed comfortably. Usually this requires 90% return of strength compared to the contralateral knee.

Grade 1 and 2 sprains often allow return to play within 1-2 weeks. Grade 3 injuries usually require at least 6 weeks for return to play, although some authors have reported 3-4 weeks.


Prophylactic bracing is controversial, although many athletes wear braces. Some studies recommend bracing after showing a decrease in injury rate. Older studies did not show a decrease in injuries, and some actually demonstrated a slightly increased rate of injuries.



Medication Summary

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Nonsteroidal anti-inflammatory drugs

Class Summary

Have analgesic, anti-inflammatory, and antipyretic activities. Their mechanism of action is not known, but they may inhibit cyclooxygenase 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 (Ibuprin, Motrin)

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

Naproxen (Anaprox, Naprosyn, Naprelan, Aleve)

For relief of mild to moderate pain; inhibits inflammatory reactions and pain by decreasing activity of cyclooxygenase, which results in a decrease of prostaglandin synthesis.

Ketoprofen (Orudis, Oruvail, Actron)

For relief of mild to moderate pain and inflammation.

Small dosages are initially indicated in small and elderly patients and in those with renal or liver disease.

Doses >75 mg do not increase therapeutic effects. Administer high doses with caution and closely observe patient for response.

Sulindac (Clinoril)

Decreases activity of cyclooxygenase and in turn inhibits prostaglandin synthesis. Results in a decreased formation of inflammatory mediators.


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 have sustained injuries.

Propoxyphene/acetaminophen (Darvocet N-100)

Drug combination indicated for mild to moderate pain.

Acetaminophen (Tylenol, Feverall, Aspirin-Free Anacin, Tempra)

DOC for pain in patients with documented hypersensitivity to aspirin or NSAIDs, with upper GI disease, or who are taking PO anticoagulants.

Codeine/acetaminophen (Tylenol and codeine)

Indicated for the treatment of mild to moderate pain.

Hydrocodone and acetaminophen (Vicodin, Lortab, Norcet, Margesic)

Drug combination indicated for moderate to severe pain.

Hydrocodone and ibuprofen (Vicoprofen)

Drug combination indicated for short-term (< 10 d) relief of moderate to severe acute pain.

Oxycodone and acetaminophen (Percocet, Roxilox, Roxicet, Tylox)

Drug combination indicated for the relief of moderate to severe pain.