Lateral Collateral Knee Ligament Injury

Updated: Nov 30, 2020
Author: Sherwin SW Ho, MD; Chief Editor: Sherwin SW Ho, MD 


Practice Essentials

Lateral collateral ligament (LCL) injuries result from a varus force across the knee. A contact injury, such as a direct blow to the medial side of the knee, or a noncontact injury, such as a hyperextension stress, may result in a varus force across the knee injuring the LCL. In terms of functionality, the LCL has often been grouped with the popliteofibular ligament and the popliteus tendon as the posterolateral corner (PLC). See the image 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

Signs and symptoms

Symptoms of LCL injuries include the following:

  • Pain
  • Difficulty on uneven ground
  • Swelling
  • Ecchymosis

Patients may also describe paresthesia as well as a foot drop if injury to the peroneal nerve has occurred.

See Presentation for more detail.


Radiography of the knee should always be the initial imaging modality. Magnetic resonance imaging (MRI) is an important diagnostic tool for evaluating the LCL as well as the structures of the PLC.

If a multiligamentous knee injury or a knee dislocation is suspected, an arteriogram may be necessary to rule out an arterial injury.

See Workup for more detail.


Grade I and II injuries can usually be treated nonoperatively. Grade III tears of the LCL involve disruption of the PLC and are best treated with surgical intervention to prevent instability.

See Treatment for more detail.

Functional Anatomy

The LCL is a round ligament that originates close to the lateral epicondyle and inserts onto the fibular head.

Sport-Specific Biomechanics

Varus stress

The LCL is the primary restraint to varus stress across the knee.

External tibial rotation

The PLC, which includes the LCL, popliteofibular ligament, and popliteus tendon, is the primary restraint to external rotation stress across the knee.


An LCL injury may be caused by a direct blow to the anteromedial aspect of the knee or a noncontact varus or hyperextension injury.

An LCL injury may occur concomitantly with other ligamentous injuries in the setting of a multiple ligamentous knee injury as a result of a significant trauma, such as a motor vehicle accident or a fall from height.


With proper treatment and rehabilitation, the prognosis for LCL injuries is good to excellent.


Potential complications of LCL injuries are listed below:

  • Chronic pain

  • Weakness

  • Instability

  • Peroneal nerve injury

Patient Education

For patient education resources, see What Are Knee Ligament Injuries? and Workout Injuries: Prevention and Treatment, as well as Knee Injury.




Patients often describe a discrete event that caused the injury. A direct blow to the anteromedial aspect of the knee is a common injury mechanism for the PLC. Noncontact varus stresses as well as hyperextension stresses can also cause injuries to these structures.

The severity of injury should be delineated if acutely evaluating a patient. Significant ligamentous injuries to the knee that result in knee instability or dislocation have been associated with vascular injuries that may distally compromise perfusion of the limb.

Symptoms include pain, difficulty on uneven ground, swelling, and ecchymosis. Patients may also describe paresthesias as well as a foot drop if injury to the peroneal nerve has occurred.

A complete history including age, occupation, recreational activities, lifestyle, and interests should be obtained. Previous knee symptoms, injuries, or surgeries should also be elicited.

Physical Examination

The extremity should be evaluated for alignment, ecchymosis, skin abrasions, open wounds, and effusion.

Palpate the joint line, quadriceps insertion, patella, patellar tendon origin and insertion, lateral epicondyle, and fibular head. Palpate the suprapatellar pouch for effusion.

Perform a neurovascular examination that includes evaluation of the dorsalis pedis and posterior tibialis pulses. Evaluate the ankle plantar flexion and dorsiflexion, as well as foot eversion and inversion. (See also the Medscape Reference article Foot Drop.)

If a knee dislocation is suspected, the ankle brachial index should be determined. Values less than 0.9 should warrant an arteriogram and vascular surgery consultation to evaluate for arterial injury.

Examine passive and active range of motion of the knee.

Examine the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), and medial collateral ligament (MCL).

To specifically isolate the LCL, apply a varus stress to the knee at 30º of flexion. Evaluate the amount of opening as well as the presence or absence of an endpoint. Ligamentous injuries can be graded as follows[1, 2] :

  • Grade 1 – Interstitial injury without laxity is present, but pain occurs 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.

Compare examination to uninvolved extremity.





Imaging Studies and Other Tests

Imaging studies

Radiography of the knee should always be the initial imaging modality. Three views of the knee consisting of anteroposterior (weight-bearing if patient is able to tolerate), lateral, and Merchant views are obtained. Findings include varus malalignment when standing, dislocation, subluxation, fracture, quadriceps tendon disruption, patellar tendon disruption, and arthritis.

MRI is an important diagnostic tool for evaluating the LCL as well as the structures of the posterolateral corner. Cartilage, cruciates, and menisci can also be evaluated with an MRI study.

A study was conducted to describe normative values of the thicknesses of the LCL and popliteus tendon in patients who underwent knee surgery but had no evidence of knee instability. The study concluded that even in patients without varus and posterolateral rotary instability, signal alteration and thickening of the LCL and/or popliteus tendon can be frequently found with MRI. In particular, abnormal MRI findings of the LCL were likely to be more frequent in the patients with more varus knee alignment.[3]

Other tests

In cases of suspected multiligamentous knee injury or knee dislocation, an arteriogram may be necessary to rule out suspected arterial injury.



Acute Phase

Rehabilitation program

Physical therapy

Grade I and II injuries can usually be treated nonoperatively.[4] Knee bracing with the knee locked in full extension is advised. Full weight bearing can be performed with the knee brace in place. The patient should perform knee range of motion exercises in the prone position only. After 4-6 weeks, patients may return to sport-specific therapy, only if strength and range of motion are comparable to the uninjured side.

Surgical intervention

Grade III tears of the LCL involve disruption of the posterolateral corner (PLC) and are best treated with surgical intervention to prevent instability.[5, 6]

Recovery Phase

Rehabilitation program

Physical therapy

Physical therapy consists of early range-of-motion (ROM) exercises.



Medication Summary

Short-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) is acceptable for treating the symptoms of LCL injury.

Nonsteroidal anti-inflammatory agents (NSAIDs)

Class Summary

Although most NSAIDs are used primarily for their anti-inflammatory effects, they are effective analgesics and are useful for the relief of mild to moderate pain. Any prescription-strength NSAID can be effective. For patients who cannot tolerate the early-generation NSAIDs because of gastrointestinal (GI) intolerance, they may benefit from cyclooxygenase-2 (COX-2) inhibitors (eg, celecoxib [Celebrex], Pfizer Inc, New York, NY).

Ibuprofen (Motrin, Ibuprin, Advil)

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

Diclofenac (Voltaren)

Inhibits prostaglandin synthesis by decreasing activity of enzyme cyclooxygenase, which in turn decreases formation of prostaglandin precursors.

Sulindac (Clinoril)

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

COX-2 Inhibitors

Class Summary

Although increased cost can be a negative factor, the incidence of costly and potentially fatal GI bleeding is clearly less with COX-2 inhibitors than with traditional NSAIDs. Ongoing analysis of the cost avoidance of GI bleeds further defines the populations that will find COX-2 inhibitors the most beneficial.

Celecoxib (Celebrex)

Inhibits primarily COX-2. COX-2 is considered an inducible isoenzyme that is induced during pain and inflammatory stimuli. Inhibition of COX-1 may contribute to NSAID GI toxicity. At therapeutic concentrations, COX-1 isoenzyme is not inhibited; thus, GI toxicity may be decreased. Seek lowest dose of celecoxib for each patient.



Return to Play

The time frame for return to play depends on the severity of the LCL injury and concomitant injuries. Early goals of therapy are to prevent stiffness of the knee while allowing healing to take place. Later, sport-specific therapy is started to transition the athlete into full participation. The athlete needs to regain strength and functional rehabilitation, including proprioception, sport-specific activity, and some type of dynamic running program.

Functional testing (eg, one-legged balance, jumping, running, cutting) should be completed to evaluate the overall condition of the knee. Athletes should be pain free with functional activities and regain full strength and range of motion before they return to sports.


Knee bracing has not been shown to be effective in preventing LCL injuries. A program directed at improving flexibility and strength of the core musculature may lessen the likelihood of lower extremity sporting injury.