Lateral collateral ligament injury and related posterolateral corner injuries of the knee

INTRODUCTION — Isolated injuries of the lateral collateral ligament (LCL) are among the least common knee injuries but can occur when the joint is struck from the inside (varus stress). More commonly, and typically as the result of more significant trauma, the LCL is injured along with other structures, often including those of the posterolateral corner of the knee but also possibly the anterior or posterior cruciate ligaments. The care of uncomplicated, minor LCL injuries can be supervised by primary care clinicians, but more severe injuries warrant orthopedic referral.

The presentation, evaluation, diagnosis, and nonoperative management of LCL injuries are reviewed here. Other knee injuries and an overall approach to knee complaints in active adults are discussed separately.

●Knee pain (see "Approach to the adult with unspecified knee pain" and "Approach to the adult with knee pain likely of musculoskeletal origin")

●Knee ligament injury (see "Anterior cruciate ligament injury" and "Medial (tibial) collateral ligament injury of the knee" and "Posterior cruciate ligament injury")

●Other knee injuries (see "Meniscal injury of the knee" and "Patellofemoral pain" and "Quadriceps muscle and tendon injuries" and "Iliotibial band syndrome" and "Hamstring muscle and tendon injuries")

BIOMECHANICS — The lateral collateral ligament (LCL) works in concert with the other soft tissue structures of the arcuate ligament complex to provide posterolateral stability to the knee, including prevention of medial translation of the tibia [1]. The primary posterolateral stabilizing structures are commonly considered to be the LCL, popliteus tendon, and the popliteofibular ligament (PFL). Other stabilizing structures include the biceps femoris and lateral gastrocnemius muscles and tendons; and the popliteal meniscal, fabellofibular, oblique popliteal, and arcuate ligaments [2].

In addition, as an independent structure, the LCL acts as a barrier to varus instability throughout all angles of knee flexion [3]. The LCL may also act with the other primary posterolateral structures to prevent posterior translation [4] and external rotation of the tibia on the femur during early knee flexion (0 to 30 degrees) [5,6]. As knee angles increase beyond 60 degrees, the LCL provides less restraint against external rotation compared to the PFL [6], and beyond 70 degrees, it does not provide significant resistance to external rotation [7].

EPIDEMIOLOGY — Injury to the lateral collateral ligament (LCL) represents approximately 8 percent of all knee injuries, making it the second least commonly injured knee ligament, with the posterior cruciate ligament (PCL) being the least injured [8]. Of the knee injuries treated in this study of high school athletes, the LCL was involved in 2.5 percent of cases. In a large series of knee injuries with hemarthrosis, only 2 percent had isolated tears of the LCL or PLC, and 87 percent of involved multi-ligament injuries (eg, anterior cruciate ligament [ACL], PCL) [9]. In a large retrospective study, approximately 48.9 percent of cases involving LCL injuries were treated with surgery; half of these cases involved multiple ligament injuries [10]. Approximately 25 percent of LCL injuries in the pediatric and adolescent populations also involve injury to the posterolateral corner [11]. .

RISK FACTORS — It is difficult to draw conclusions regarding which activities and sports pose the greatest risk, given the relative rarity of isolated lateral collateral ligament (LCL) injuries. However, several risk factors for knee injuries generally have been identified. Female gender, sports competition (versus practice), higher rates of player-to-player contact, and participation in sports that involve significant pivoting, jumping, and landing are associated with higher knee injury rates [8]. Among 20 popular high school sports in the United States, American football has the highest overall knee injury rate (6.29 per 10,000 athlete exposures). According to a large, retrospective Swiss study, soccer (football) and skiing accounted for the largest number of knee injuries, but tennis and gymnastics involved the largest number of LCL injuries, although such injuries were relatively uncommon [10]. Risk factors for soft tissue injuries of the knee of all types among United States Army soldiers include prior knee injury, increasing length of service, increasing age, prior combat deployment, infantry occupation, prior ankle injury, and prior hip injury [12].

CLINICAL ANATOMY — The soft tissue structures about the lateral knee, often termed the "lateral complex," are arranged in layers that may appear indistinguishable. Layers of the lateral complex, from superficial to deep, include:

●First layer – Iliotibial band, superficial portion of biceps femoris (figure 1 and figure 2)

●Second layer – Lateral collateral ligament (LCL) (picture 1 and figure 3)

●Third layer – Joint capsule, arcuate ligament, popliteofibular ligament, popliteus tendon (figure 4)

●Overall properties of the LCL – The LCL typically measures approximately 5.3 +/- 10 mm in width [13] and 60 mm in length, and is more cord-like and thicker than the fan-like medial collateral ligament (MCL) [14]. Varus-oriented static alignment, older age, and heavier body weight are all factors associated with thicker LCLs [13]. The stiffness of the two collateral ligaments is comparable, although the tensile strength of the LCL is half that of the MCL [15]. Unlike the MCL, the LCL does not attach to the meniscus or joint capsule because of the intervening popliteus tendon.

●Origin and insertion – The LCL originates on the lateral femoral condyle on the external tuberosity at a point just anterior to the lateral head of the gastrocnemius muscle [2]. There are three known variations for the origin of the LCL:

•Apex of the lateral epicondyle

•Fovea posterior to the lateral epicondyle

•Posterior and proximal to the lateral epicondyle, posterior to origin of popliteal tendon

Injuries to the last two locations share equal prevalence [16,17]. After traversing the posterolateral joint line extra-articularly, the LCL inserts on the anterior point of the fibular head as a component of the conjoined tendon along with the biceps femoris tendon [18].

●Examination landmarks – The LCL can be palpated with the patient in the supine position and the knee flexed 90 degrees. The ligament becomes more prominent in the "figure four" position (knee flexed 90 degrees and hip externally rotated to place the ankle on the contralateral lower leg). Alternatively, the patient can be placed in a supine position with their knee flexed to 90 degrees and feet flat on the table without hip rotation. This alternative position can be useful in patients with limited hip or knee mobility.

Because of the potential difficulty differentiating among the LCL, biceps femoris tendon, and iliotibial band at the joint line, the examiner should begin palpation at the ligament’s origin on the external femoral condyle and follow the cord-like LCL distally as it courses across the joint line towards the fibular head.

●Variations in pattern/shape – Although the most common morphology of the LCL is cord type, present in 69 percent of knees, there are multiple less-common variations. These include [19]:

•Band type: 26 percent

•Mixed (band and cord): 2 percent

•Y-shaped: 2 percent

●Anterolateral ligament (ALL) – In approximately 9 percent of individuals, the LCL is reinforced with an accessory ALL that helps to prevent excessive internal tibial rotation [19]. The ALL originates at the lateral femoral epicondyle, with arms extending to the fibular head (fibular attachment) and posterior aspect of Gerdy's tubercle (tibial attachment).  

●Blood and nerve supply – Blood supply to the LCL is from the genicular network of arteries that arise from the popliteal artery, with primary contributions from the superior and inferior lateral genicular arteries (picture 2). Innervation of the LCL varies among individuals. Both the tibial nerve and common peroneal (fibular) nerves (figure 5) provide innervation [20].

MECHANISM OF INJURY — Isolated injuries of the lateral collateral ligament (LCL) are relatively uncommon. Because of the close proximity of the second and third layers of the lateral complex, most LCL injuries occur in association with injuries to the posterolateral corner (PLC), posterior cruciate ligament (PCL), and/or anterior cruciate ligament (ACL) [21]. The most common mechanism of injury producing multi-ligament knee injury involves a high energy force that combines hyperextension and varus moments (eg, knee forced laterally from a blow to the medial side) [21]. Alternatively, injury may occur with an isolated varus hyperextension or external tibial rotation force. Typically, an isolated LCL injury, especially of lower grade, is caused by a primarily varus force.

Injuries that may occur in association with an LCL tear include:

●Soft tissue structures of the posterolateral corner

●Anterior cruciate ligament (see "Anterior cruciate ligament injury")

●Posterior cruciate ligament

●Lateral meniscus (see "Meniscal injury of the knee")

CLINICAL PRESENTATION AND EXAMINATION

Common presentations — Patients who have sustained a lateral collateral ligament (LCL) injury typically present following a blow to the medial or anteromedial aspect of their knee while it was fully extended, and report lateral or posterolateral knee pain. The prototypical example is of an American football player who, in the process of being tackled, is struck in the knee, which sustains a posterior varus shift while the foot is planted and knee hyperextended.

Alternatively, patients can sustain a noncontact LCL injury from a sudden varus moment (knee bending laterally) while the knee is hyperextending. Olympic weightlifters with poor lateral knee stability can sustain this type of injury during heavy lifts. Both contact and noncontact LCL injuries can involve varying degrees of tibial rotation as a component of the injury force. Patients often describe a sense of knee instability when ambulatory or stationary.

Following an LCL injury, patients may experience one or several mechanical knee symptoms, including:

●Swelling

●Locking or catching with movement (if meniscal injury is also involved)

●Giving out under stress or with any rapid motion while bearing weight (eg, moving from side to side, rotating the knee)

●Sense of instability with performing cutting movements (change of direction at speed)

Examination findings — On initial inspection (figure 2), patients with an LCL injury (particularly those involving the posterolateral corner [PLC]) may demonstrate a "varus thrust gait" as the LCL fails to maintain stability and prevent excessive lateral opening. A varus thrust gait can be observed during foot strike when a gap develops in the lateral side of the knee and the patient shifts their weight to reduce their knee back to normal alignment.

Another compensatory gait pattern in which the patient maintains a flexed knee and does not allow it to reach full extension can be seen in the LCL injured patient. During the swing phase, the patient may demonstrate excess internal rotation of their tibia, and avoid complete extension of their knee in an effort to avoid a feeling of instability. During the stance phase, genu recurvatum from a hyperextended knee may be observed.

The most common examination finding in patients with an LCL injury is tenderness along the lateral knee (picture 3). Localized soft tissue swelling may be appreciated at the site of injury.

Varus stress testing (described separately) at both full extension and 30 degrees of knee flexion is the most useful initial test to assess the severity of an LCL injury (picture 4). The clinician should assess for laxity relative to the contralateral knee and for focal pain provoked by the maneuver. (See "Physical examination of the knee".)  

Additional special tests that can be used to help confirm the presence of a more complicated posterolateral soft tissue injury include the four listed below [22,23]. The test characteristics of these maneuvers are not well studied, but when in agreement (ie, all positive or all negative) they can help to rule in or rule out PLC injury. However, for the patient in pain, it may not be feasible to perform all four maneuvers. Many experienced clinicians rely on the posterolateral drawer test and the dial test.

●External rotation recurvatum test – With the patient in a supine position, the examiner provides a stabilizing force to the femur by applying downward pressure at the level of the quadriceps tendon (suprapatellar). Next, the examiner uses their contralateral hand to lift the great toe upward while externally rotating the tibia. Excessive motion compared with the contralateral knee is indicative of posterolateral rotatory instability. A positive external rotation recurvatum test raises the possibility of an anterior cruciate ligament (ACL) injury and the ACL should be carefully examined [24]. (See "Anterior cruciate ligament injury", section on 'Physical examination'.)

●Posterolateral drawer test – With the patient supine (with knee flexed 90 degrees, foot flat on table, and tibia externally rotated 15 degrees), the examiner introduces a combined posterior and external rotation force through the proximal tibia while observing the rotation of the tibial tubercle in reference to the femur (picture 5) [25]. Excessive rotation compared with the asymptomatic side suggests a high-grade PLC injury, often with popliteofibular ligament and/or popliteal tendon involvement.

●Reverse shift test – After placing the patient in the position described above for the posterolateral drawer test, the examiner extends the knee while applying a valgus and external rotation force [26]. In the presence of a severe PLC injury, the iliotibial band can be seen reducing the posteriorly subluxed tibia.

●Dial test (30, 90 degrees) – With the patient prone, hold their feet and passively rotate the tibia externally, first with the knees at 30 degrees of flexion and then at 90 degrees of flexion (picture 6). A difference of more than 10 to 15 degrees of external rotation compared with the uninjured side suggests PLC injury. (See "Physical examination of the knee", section on 'Tests for PCL injury and posterior stability'.)

Although these tests are useful for the diagnosis of a combined LCL-PLC injury, a positive maneuver may stem from an isolated PLC injury without LCL involvement [27]. Observational evidence suggests that physical examination findings correlate poorly with magnetic resonance imaging (MRI)-confirmed LCL injuries [28].

Associated injuries — Injuries that occur in association with an LCL tear can include the following structures:

●Soft tissue structures of the posterolateral corner, including popliteus

●Anterior cruciate ligament

●Posterior cruciate ligament

●Lateral meniscus

Given how often LCL tears occur in association with other significant knee injuries, the clinician should examine all these structures in any patient with lateral knee pain following trauma, except when this is not possible due to the extent of injury or degree of pain.

Lateral knee trauma may involve injury of the common peroneal or superficial peroneal nerve, which may necessitate additional treatment. Therefore, it is important to assess sensation and lower extremity strength (dorsiflexion, eversion) in all patients presenting with lateral knee symptoms following injury. As partial injury of the peroneal nerves may be subtle, it can be useful to observe the patient’s gait while watching specifically for a foot drop. Inability to maintain dorsiflexion of the foot during heel walking may reveal a more subtle foot drop that is not observed on casual ambulation.

Classification of LCL injury

●Grade 1 – Mild sprain

•Grade 1 injuries of the LCL result in localized tenderness. Laxity and mechanical symptoms are not present. They are associated with localized subcutaneous swelling at the mid-substance and/or insertions of the ligament.  

●Grade 2 – Partial tear

•Grade 2 injuries of the LCL involve a partial-thickness tear and associated swelling, resulting in tenderness that may be localized or more diffuse along the lateral and posterolateral knee. Some swelling may be present. Mild to moderate laxity can be observed (5 to 10 mm), but the ligament has a solid endpoint.

●Grade 3 – Complete tear

•Grade 3 injuries of the LCL involve a full-thickness tear of either the midsubstance or one of the insertions and cause varying degrees of pain. There is typically laxity (>10 mm) without a solid endpoint and the patient experiences one or more mechanical symptoms. These injuries are often associated with posterolateral corner (PLC) pathology.

Often the extent of injury is difficult to determine and the exact grading of an LCL injury is not always clear. This is especially true in the setting of an acute knee injury where pain and swelling can make examination maneuvers less reliable. Therefore, it is appropriate to treat all but the mildest acute LCL injuries as grade 3 initially. (See 'Initial treatment' below.)

IMAGING

Approach to imaging — In cases of minor knee trauma involving otherwise healthy individuals where we suspect an isolated, low-grade lateral collateral ligament (LCL) injury, we generally do not perform imaging studies, aside from a bedside musculoskeletal ultrasound, which we perform in nearly all patients with a suspected knee injury. In cases involving more significant trauma to the knee, we generally obtain plain radiographs as described immediately below, in addition to performing an ultrasound examination. We obtain a magnetic resonance imaging (MRI) study of the knee, if available, in all cases of significant knee trauma in which the history, examination, or ultrasound findings suggest that major injury involving the LCL and other structures (eg, cruciate ligament, meniscus) may have occurred.

Radiographs — Damage to the LCL cannot be seen on plain radiographs. However, we obtain anteroposterior and lateral views of the knee in all cases involving more than minor knee trauma when an LCL injury is suspected, and especially if there is bony tenderness of the medial aspect of the femur, tibia, or patella. In addition, the Ottawa Knee Rules stipulate that tenderness at the fibular head is an indication for knee radiographs [29].

The arcuate sign, a small avulsion fracture (<1 cm) of the styloid of the proximal fibula (image 1), is considered pathognomonic for posterolateral corner (PLC) injury and should alert the clinician to the possibility of a distal LCL avulsion [30]. As high-grade soft tissue injuries are common in the presence of an arcuate sign, clinicians should follow up with advanced imaging (eg, MRI) to characterize the extent of injury [31].

The Segond fracture, an avulsion fracture of the lateral tibial plateau classically associated with anterior cruciate ligament (ACL) injury, can also indicate an LCL injury (image 2 and image 3). This fracture is the result of a varus force that causes the oblique attachment of the LCL on the lateral tibia (the anterior oblique band) to avulse a fragment from the tibial plateau.

Chronic lateral knee instability may manifest as degenerative changes in the lateral compartment (image 4) visible on radiographic imaging.

Varus stress radiographs — The addition of varus stress views can be helpful in the diagnosis of lateral knee injury. These views are especially helpful for identifying varus instability and making the diagnosis of lateral soft tissue injury in the absence of magnetic resonance and ultrasound imaging. Evidence is limited, but in one biomechanical study, an increase in the lateral joint line of 2.7 mm between the resting knee and the knee placed under a varus stress was associated with an isolated LCL injury. An increase of 4 mm or more was associated with a grade 3 PLC injury [32].

Magnetic resonance imaging — Magnetic resonance imaging (MRI) is a useful tool in the assessment of suspected LCL and PLC injuries (image 5). In small observational studies using surgical findings as the gold standard, the sensitivity of MRI for detecting LCL tears ranged from 55 to 94 percent, and specificity ranged from 68 to 100 percent [33-35]. The accuracy for detecting distal biceps femoris tendon injury ranged from 87 to 95 percent [33,34], and for detecting popliteus tendon injury, 82 to 90 percent (image 6) [33,35]. Accuracy for detecting LCL and PLC injuries is higher for isolated injuries than multi-ligament injuries and for injuries sustained acutely (less than 12 weeks) compared with chronic injuries [33,35-38].

Musculoskeletal ultrasound — Musculoskeletal ultrasound (US) can be used to perform a dynamic assessment at the bedside, aiding diagnosis of an injured LCL. The LCL with a grade 1 or 2 injury appears thickened and hypoechoic. A grade 3 injury shows hypoechoic thickening of the LCL, lack of fiber continuity, associated hemorrhage and edema, and dynamic laxity of the lateral joint line. According to a small prospective study, widening of more than 10 mm of the lateral knee joint line when a varus stress is applied correlates with a need for surgical repair in all cases [39].

DIAGNOSIS — A preliminary diagnosis of lateral collateral ligament (LCL) injury is made based upon a suggestive history and correlative physical examination findings. A history of contact or non-contact trauma to the knee involving hyperextension, varus stress, and/or external tibial rotation suggests an LCL injury. The most common examination finding is tenderness along the lateral knee (picture 3); varus stress testing may reveal joint widening. Clinicians facile with musculoskeletal ultrasound often use it to confirm the diagnosis. Although not always needed for mild injuries, a definitive diagnosis can be made with magnetic resonance imaging.

INDICATIONS FOR ORTHOPEDIC CONSULT OR REFERRAL — Published evidence is lacking, but based upon our clinical experience and the opinions of a number of orthopedic surgeons and resources, we believe the following approach to orthopedic referral is reasonable. Acute lateral collateral ligament (LCL) tears associated with functional instability or injuries of the posterolateral corner or other soft tissues should be referred to an orthopedic surgeon within two weeks because surgical reconstruction is often needed. Acute, mid-portion, complete LCL tears without functional instability or associated injuries should be evaluated by a surgeon within the same period of time.

Chronic LCL injuries with persistent symptomatic instability despite appropriate rehabilitative treatment and bracing should be referred to an orthopedic surgeon.

●Indications for orthopedic consultation in the acute setting:

•LCL tear with presence of functional instability (grade 3 injuries)

•Posterolateral corner injury

•Mid-portion, compete LCL tears with or without associated injuries and functional instability

●Indications for orthopedic consultation in the follow-up setting:

•Grade 1 or 2 injuries that fail to progress or worsen after four weeks of conservative management

DIFFERENTIAL DIAGNOSIS

Acute injuries

Lateral meniscus tear — Nonspecific mechanical symptoms, such as popping, locking, buckling, and swelling are associated with several types of knee injuries, including lateral collateral ligament (LCL) and meniscal tears. Both injuries are associated with joint line tenderness. Unlike LCL injuries, a meniscal tear is often associated with a positive McMurray test (picture 7) and Thessaly maneuver. In addition, tenderness from an LCL injury is often longitudinal directly over the course of the ligament, whereas tenderness from a meniscal injury is generally circumferential (coronal plane) along the joint line. Examination techniques for the diagnosis of meniscal injuries are discussed separately. (See "Meniscal injury of the knee", section on 'Physical examination'.)

Knee (tibiofemoral) dislocation — Knee dislocations generally occur from high-energy trauma and produce gross deformity. Often, significant hemarthrosis and ecchymosis are present. However, some reduce spontaneously prior to medical assessment and may be missed. Knee dislocation typically injures multiple ligaments, possibly including the anterior and posterior cruciates. A high index of suspicion should be maintained for neurovascular injury whenever knee dislocation is considered, as intimal tears of arteries may not cause immediate vascular compromise but present late with critical limb ischemia. (See "Knee (tibiofemoral) dislocation and reduction".)

Multi-ligament knee injuries — When the LCL or the posterolateral corner of the knee is injured, the risk of concomitant injury to other knee ligaments is high. Clinicians should look closely for such injuries. Details pertaining to other knee ligaments are discussed immediately below.

●Anterior cruciate ligament (ACL) injury – Both anterior cruciate ligament (ACL) and LCL tears can present with acute knee pain, swelling, and instability, and cause tenderness along the lateral aspect of the knee. ACL tears are distinguished initially by positive special tests (eg, anterior drawer (picture 8) and Lachman (picture 9)). Examination techniques for the diagnosis of ACL injuries are discussed separately. (See "Anterior cruciate ligament injury", section on 'Physical examination'.)

●Posterior cruciate ligament (PCL) injury – Acute posterior cruciate ligament (PCL) injuries can present with symptoms like those associated with LCL tears. In addition, PCL and posterolateral corner (PLC) injuries can occur concomitantly, further complicating diagnosis. It is important to perform a systematic assessment of the PLC using the maneuvers described in the examination section above, as well as tests designed to detect PCL injury (eg, posterior drawer (figure 6), sag sign (picture 10), quadriceps active test (figure 7 and movie 1)). Knee injuries involving the PCL and PLC are typically severe and advanced imaging is necessary. Examination techniques for the diagnosis of PCL injuries are discussed separately. (See "Physical examination of the knee", section on 'Tests for PCL injury and posterior stability' and "Posterior cruciate ligament injury".)

Popliteus injury — Acute and chronic popliteus tendinopathy manifests as pain at the posterolateral aspect of the knee and is made worse with downhill walking or running and foot pronation. Whereas LCL injuries can cause pain at the lateral femoral epicondyle, popliteus injuries cause pain at the origin of the popliteus, which is just distal to the lateral femoral epicondyle.

Testing of the popliteus includes the “shoe removal maneuver,” which is performed by having the patient internally rotate the affected leg and use their toes isometrically to push the shoe off of the contralateral heel. The test is considered positive if the patient’s pain is reproduced while performing the maneuver [40].

Another examination maneuver that can be employed to diagnose popliteus injury is the Garrick test. For this test, the symptomatic knee and ipsilateral hip are flexed to 90 degrees, and then the examiner externally rotates the tibia as the patient resists with internal rotation. Reproduction of posterior knee pain suggests injury [41].

Physis (growth plate) injury — Acute knee pain in a pediatric patient may stem from a physis injury. Although often difficult to diagnosis in the setting of generalized pain and negative radiographs, physis injuries manifest tenderness along the physis. In contrast, LCL injuries cause pain and tenderness along the ligament and not along any physis.

It is worth noting that in the skeletally immature patient, bone injuries occur more commonly than tendon or ligament injuries, and posterolateral knee injuries are no exception. Consequently, in children the emphasis should be on ruling out bony injury, to include the physis, rather than diagnosing an LCL injury. (See "General principles of fracture management: Fracture patterns and description in children", section on 'Physeal (growth plate)' and "General principles of fracture management: Fracture patterns and description in children", section on 'Physeal fracture description'.)

Bone contusion — Depending on the location, an acute bone contusion can easily mask as an LCL injury. Precise palpation of the painful structure is paramount in differentiating the two entities. Bone contusions, if located laterally, do not result in worsening of pain with varus stress testing.

Proximal tibiofibular syndesmosis injury — Case reports describe the so-called "parachute jumper’s knee," in which a patient lands on an externally rotated, dorsiflexed foot while their knee is in flexion [42]. With such injuries, pain and swelling develop over the lateral knee. Pain can be reproduced by translation of the fibular head in an anteroposterior direction, a finding not seen in LCL injuries. Proximal tibiofibular syndesmosis injury can occur concomitantly with a distal tibiofibular syndesmosis injury or tibial fracture. A syndesmosis injury can result in a falsely positive varus test, as the fibular head moves with varus stressing. Conversely, a proximal fibular fracture (which also manifests as lateral pain and swelling) does not produce a positive varus test unless the fracture is complete and displaced.

Chronic injuries

●Meniscal injury — Long-standing lateral meniscal pathology can mask a chronic LCL injury. Varus stress testing is the key examination maneuver for distinguishing between these diagnoses. Whereas such testing causes increased pain and widening of the lateral joint line in the knee with an LCL injury, pain remains unchanged or improves in the knee with a lateral meniscal injury. (See "Meniscal injury of the knee".)

●Iliotibial band syndrome — Iliotibial band syndrome (ITB) can often be distinguished from LCL injury based on the history. Unlike LCL injuries, ITB syndrome is typically not associated with any specific incident but develops gradually. Pain is typically reported to be at the distal lateral femoral epicondyle and can be reproduced and exacerbated by applying pressure at this location while cycling the knee between extension and flexion (Nobles test). Varus stress testing does not cause pain with ITB syndrome. (See "Iliotibial band syndrome".)

●Popliteus tendinopathy — The means for distinguishing LCL injury and popliteus tendinopathy are described above. (See 'Popliteus injury' above.)

INITIAL TREATMENT — Lateral collateral ligament (LCL) injuries are treated initially with standard interventions, including icing, compression, and analgesics. Care should be given to avoid cold injury to the common peroneal nerve in the posterolateral knee by applying ice no longer than 15 minutes at a time or by using ice massage rather than continuous application, usually no more often than every two hours. When the injury grade is unclear, we recommend 48 to 72 hours of rest, ice, compression, and protection with a knee immobilizer while awaiting definitive imaging and reevaluation. Optimally, however, an early determination of injury grade will provide prognostic information and allow early treatment.

Protection of the injured posterolateral structures from further injury is important for treatment. This assists in pain control, healing, and prevention of further injury. We use the following approach:

●Grade 1 – Crutches for up to a week if needed for pain control; hinged bracing (medial and lateral stabilization but allowing flexion and extension) for four to five weeks during all weight-bearing.

●Grade 2 – Crutches and knee immobilizer for one to three weeks for pain control, then progress from non-weight-bearing to partial-weight-bearing in weeks two or three. A hinged brace may be used once the patient is partial-weight-bearing, usually at two to three weeks.

●Grade 3 – Immobilization, non-weight-bearing with crutches, and consultation with an orthopedic surgeon. Immobilization will likely be maintained until surgery is performed, preferably within two weeks of injury. Relative to comparably severe injuries of the medial collateral ligament, healing of severe LCL injuries is more problematic, and there is a lower threshold for surgical management [15]. (See "Medial (tibial) collateral ligament injury of the knee".)

In an observational study of 43 patients with isolated LCL injury, reconstructive surgery resulted in high patient satisfaction and significant improvement in knee function [43]. An average of 22 days passed from the time of injury to surgery. Surgical repair is of greater importance when additional injuries to supporting structures have occurred in addition to the LCL.

Referral to physical therapy for a formal rehabilitation program may be useful, especially for patients with grade 2 injuries or post-operative grade 3 injuries. The specific program must account for deficits in the patient’s functional range of motion, strength, and coordination as well as any secondary conditions such as peroneal nerve injury.

Although surgery is generally recommended when knee instability is present, there is at least one case report of successful conservative management, consisting of selective functional strengthening, proprioceptive training, and the gradual introduction of graded sport-specific activities, for an isolated grade 3 injury with increased laxity in an adolescent athlete [44].

Activity must be modified to avoid cutting and pivoting movements, collisions, and any activities that cause pain. Low-impact, painless aerobic activity, such as low resistance bicycling, should be encouraged, and upper body resistance training is permitted, but lower body resistance training must be modified to avoid stressing the injured structures.

FOLLOW-UP AND DEFINITIVE CARE — Isolated grade 1 and 2 lateral collateral ligament (LCL) injuries usually do not require surgery, but early referral to physical therapy for rehabilitation is important for recovery. In contrast, any injury with functional instability or associated injuries of the posterolateral corner (PLC), menisci, anterior cruciate ligament (ACL), or posterior cruciate ligament (PCL) warrants timely referral to an orthopedic surgeon. Early surgical repair is usually required in such cases. In addition, orthopedic referral is recommended for all grade 3 LCL injuries because of the propensity for a poor outcome with conservative management [45]. Of note, not all isolated grade 3 LCL injuries result in functional instability and necessitate surgical intervention, but repair of grade 3 injuries with PLC damage may be necessary and orthopedic referral is warranted [23].

Management of grade 1 and 2 injuries is nonoperative and should include relative rest from activities that place the injured ligament at risk of reinjury. This may require restriction from competitive play for 4 to 12 weeks and modification of occupational activities. Rehabilitative exercise may begin with gentle range of motion and isometric strength exercise, and progress to isotonic strength exercise and light aerobic activity as ROM and strength improve. Whenever possible, we suggest that patients perform their rehabilitation under the supervision of a knowledgeable physical therapist or athletic trainer. A general plan for the rehabilitation of isolated, uncomplicated grade 1 and grade 2 LCL injuries is found in the attached table (table 1). During activity, patients recovering from such injuries may benefit from the added support provided by an elastic wrap or taping (picture 11). Grade 1 or 2 injuries that fail to make progress or worsen after four weeks of conservative management should be referred to an orthopedic surgeon.

Grade 1 and 2 LCL injuries should be seen for reevaluation approximately two weeks after initial assessment. This provides an opportunity for repeat examination with less guarding than is often present shortly after the injury. Concomitant injuries that were missed on initial examination may be detected at this time. At follow-up, compliance with immobilization and bracing can be assessed, and the importance of supervised rehabilitation can be emphasized. Serial imaging is not necessary, but clinicians facile with ultrasound often perform a reexamination to assess residual swelling.

After this initial follow-up visit, patients are seen approximately every two weeks for the first two months and monthly thereafter, if surveillance remains necessary to monitor progress and determine when a return to work or sport is possible. Gentle reassessment of range of motion, strength, and ligamentous laxity are useful for monitoring progress during follow-up visits.

COMPLICATIONS

Unrecognized posterolateral corner injury — Posterolateral corner (PLC) injury can be difficult to diagnose and may be missed on magnetic resonance imaging (MRI). Any patient presenting with continued posterolateral pain following trauma to the anteromedial knee despite adequate time for an isolated lateral collateral ligament (LCL) tear to heal, should be evaluated for a posterolateral corner injury. At that point, the patient should be referred for orthopedic consultation to determine the need for further imaging and treatment.

Functional instability — Without proper healing of the LCL or combined LCL-posterolateral corner injuries, recovery may be complicated by functional knee instability.

Peroneal nerve injury — Given the proximity of the common peroneal or superficial peroneal nerve (depending on individual anatomy), the trauma that caused an LCL tear or PLC injury, or the resultant swelling, may cause a localized neuropathy. Peroneal nerve palsy develops in 35 percent of PLC injuries [27]. Concomitant injury of the ACL or PCL is associated with a much higher incidence of common peroneal nerve injury, at 81 percent [46]. Paresthesias in the distribution of the peroneal nerve, or possibly prolonged foot drop, may occur with excessive cryotherapy, especially if ice is applied directly to the skin [47]. Therefore, it is important to assess sensation and lower extremity strength (dorsiflexion, eversion) in all patients presenting with lateral knee injury. Clinicians should emphasize to patients that ice should be applied only intermittently for treatment, generally for no longer than about 15 minutes every two hours, in order to prevent this complication. There are multiple reports of foot drop following cryotherapy to the lateral knee.

RETURN TO SPORT OR WORK — Criteria for return to sport include:

●Full, painless knee motion

●Quadriceps and hamstring strength that is at least 90 percent of the unaffected lower extremity

●Absence of significant tenderness of the injured structures

●Absence of ligament laxity on examination

●Ability to complete a functional activity involving physical demands similar to patient’s sport/work without significant pain

During activity, patients recovering from a lateral collateral ligament (LCL) injury may benefit from the added support provided by an elastic wrap or taping (picture 11).

In general, patients may return to play or work following LCL injury according to the following scheme:

●Grade 1: Approximately four weeks

●Grade 2: Approximately 10 weeks

●Grade 3:

•No surgery – Approximately 10 to 14 weeks

•Surgery – Surgical recovery time plus approximately 10 weeks

PREVENTION — No high-quality evidence is available to help determine the effectiveness of common measures, such as knee braces, used to prevent lateral collateral ligament (LCL) or posterolateral corner (PLC) injuries. Nevertheless, some American football teams use hinged medial-lateral knee braces for medial collateral ligament (MCL) and LCL sprain prevention despite the absence of evidence showing benefit, according to a recent systematic review [48].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Meniscal injury" and "Society guideline links: Knee pain".)

SUMMARY AND RECOMMENDATIONS

●Epidemiology and mechanism of injury – Isolated injuries of the lateral collateral ligament (LCL) are among the least common knee injuries but can occur when the joint is struck from the inside (varus stress). More commonly, the LCL is injured along with other structures, often including those of the posterolateral corner (PLC) of the knee, but also possibly the anterior or posterior cruciate ligaments, during more significant trauma. The most common mechanism of injury producing multi-ligament knee injury involves a high energy force that combines knee hyperextension and varus moments. (See 'Biomechanics' above and 'Clinical anatomy' above and 'Epidemiology' above.)

●Clinical presentation and examination – Patients typically present following a blow to the medial or anteromedial aspect of their knee while it was fully extended and report lateral or posterolateral knee pain. The knee may be swollen and the patient may describe mechanical symptoms, such as locking, catching, or giving out. Observation may reveal gait abnormalities as the patient attempts to compensate for lateral knee instability. Examination findings typically include tenderness along the lateral knee and widening of the lateral knee joint with varus stress testing (picture 4). (See 'Mechanism of injury' above and 'Clinical presentation and examination' above.)

Given how often LCL tears occur in association with other significant knee injuries, the clinician should examine all structures at risk of injury in any patient with lateral knee pain following trauma, except when this is not possible due to the extent of injury or degree of pain. These structures include the PLC, anterior and posterior cruciate ligament injuries, and the lateral meniscus. (See 'Associated injuries' above and "Physical examination of the knee".)

●Diagnosis – A preliminary diagnosis of LCL injury is made based upon a suggestive history and correlative physical examination findings. Clinicians facile with musculoskeletal ultrasound often use it to confirm the diagnosis. Although not always needed for mild injuries, a definitive diagnosis can be made with magnetic resonance imaging. (See 'Diagnosis' above and 'Imaging' above.)

●Indications for orthopedic consultation – Indications for surgical referral in the acute setting include:

•LCL tear with presence of functional instability (grade 3 injuries)

•LCL tear associated with other significant soft tissue knee injury (eg, posterior cruciate ligament tear, meniscal tear)

•Posterolateral corner injury

•Mid-portion, compete LCL tears with or without associated injuries and functional instability

Indications for orthopedic consultation in the follow-up setting include grade 1 or 2 injuries that fail to progress or that worsen after four weeks of conservative management.

●Differential diagnosis – The differential diagnosis for acute LCL injury includes lateral meniscus tear, tibiofemoral dislocation, anterior and posterior cruciate ligament tears, popliteus injury, physis injury, bone contusion, and injury of the proximal tibiofibular syndesmosis. (See 'Differential diagnosis' above.)

●Management – LCL injuries are treated initially with standard interventions, including rest, limited icing, compression, and analgesics. Weight-bearing status and the level of protection needed for the knee joint vary according to the severity of injury. The details of initial management and a plan for follow-up care are provided. Isolated, minor LCL injuries are typically managed with physical therapy; orthopedic referral is obtained for more complicated injuries involving the LCL alone or additional knee structures. (See 'Initial treatment' above and 'Follow-up and definitive care' above and 'Return to sport or work' above.)