September 12, 2021
LCL injuries

Lateral collateral ligament injuries


The lateral collateral ligament (LCL), also known as the fibular collateral ligament, is the primary varus stabilizer of the knee and isolated injuries are somewhat uncommon. In addition to the popliteus and the popliteofibular ligament, it provides stability to the posterolateral corner (PLC) of the knee.

Case Vignette

A 16 year old female soccer player presents to your clinic with left knee pain. The goalie dove into her knees to try to get the ball and she sustained a blow to her anteromedial knee by the goalie’s shoulder. She did have immediate pain and trouble walking. On examination, she does not have laxity on her Lachman test and does not have increased rotation with the dial test. There is no joint effusion. She does have 4 mm of laxity with varus stress and no laxity with valgus stress. Of the following options, what is the most likely treatment plan?

A) Orthopedic surgery referral
B) Place in knee immobilizer for 2 weeks and reassess
C) Early mobilization and physical therapy prescription
D) Order MRI of her knee

With the knee in extension, the LCL is approximately 6 cm ong and 3-5 mm thick [1]. It extends from the lateral femoral epicondyle about 2 cm above the joint line to the fibular head. The LCL and biceps femoris tendon form a conjoined tendon. There is an anterior oblique band (AOB), a band of fibrous tissue, that extends from the LCL to the lateral portion of the tibia. Some fibers of the AOB blend with the iliotibial band (ITB). It does not attach to the lateral meniscus and is described as cord-like as opposed to fan-like. Three separate LCL innervation patterns have been identified: the distal third of the thigh from the muscular branch (tibial nerve) of the biceps femoris muscle, at the level of the popliteal fossa from the common fibular nerve, and at the level of the proximal fibula from the common fibular nerve [2].
LCL Anatomy

Image 1: Lateral knee anatomic image. Adopted from [14].

The most common mechanism of injury is seen via a high-energy blow to the anteromedial knee, combining hyperextension and extreme varus force. Noncontact hyperextension and noncontact varus stressors have also been reported to cause LCL injuries [3]. Incidence in high school athletes has been reported at 7.9% of knee injuries. Another large study showed isolated LCL pathology in roughly 2 percent of injuries, which typically resulted from lower-magnitude forces. [4,5]. In a study of almost 20,000 knee injuries across a diverse number of sporting activities, isolated LCL pathology occurred in roughly 2% of injuries.12 These isolated injuries typically resulted from lower-magnitude forces, which ultimately led to lower-grade damage to the ligament proper.Although there have been few studies completed on isolated LCL injuries, reports show that female gender, high contact sports, and sports that require high velocity pivoting and jumping increase the likelihood of injury. This includes sports such as soccer, tennis and gymnastics [4]. Skiing and snowboarding have also been shown in more recent studies to have increased risks involved [15].

history and physical

The most common presenting symptom is usually an acute event with a medial or anteromedial blow to the knee while the knee is fully extended. A varus buckling is occasionally included in the presentation. The patient or athlete may complain of lateral knee pain and may even have medial knee pain if trauma was involved. There may be lower lateral extremity paresthesias as well and foot weakness or foot drop [6]. More chronic pain may present with dull lateral knee pain with a sense of instability with cutting activities.

Due to the uncommon nature of the injury, the provider must examine the knee fully and rule out other concomitant conditions, such as an ACL or PLC injury. Swelling about the lateral soft-tissue envelope of the knee is often present and can correlate with the degree of injury to the ligamentous complex [2]. There will likely be tenderness over the LCL region of the knee and at the fibular head. The LCL can be more easily evaluated for tenderness by having the patient cross their affected leg and resting the foot on the opposite knee (Img. 2). Thirty degrees is the angle at which the maximum amount of varus laxity is observed with application of 10 Nm of force and is of particular importance for clinicians during examination of the integrity of the LCL after injury. Conversely, varus laxity in full extension frequently denotes injury to one or both of the cruciate ligaments. Historically, a varus opening of less than 5 mm has signified a low-grade LCL injury, an opening of 6 to 10 mm has signified a moderate grade injury and an opening of  more than 10 mm represented a high-grade injury [7].

LCL Palpation

Image 2. Palpation of the lateral collateral ligament positioning. Adopted form [2].

The provider must be careful to rule out a PLC injury during the examination. Specific assessments for the integrity of the PLC include the dial test, the posterolateral drawer test, and the recurvatum test [7]. The dial test is best performed by comparing the amount of external rotation in each knee while the patient is in the prone position. An increase in external rotation of more than 10 degrees with the knee flexed to 30 is indicative of a PLC injury. With the posterolateral drawer test, the examiner evaluates the PLC by applying a posteriorly directed force and external rotation torque to the knee with the foot in 15 degrees of external rotation. A positive test result is indicated by increased external rotation compared with the contralateral side. The recurvatum test is performed with the knee held in extension. While stabilizing the thigh, the examiner lifts the ipsilateral great toe and measures the distance the heel can be lifted (ie, hyperextension or recurvatum). An increased distance compared with that of the contralateral knee indicates a PLC injury.


Imaging normally begins with plain radiographs and these should include weight-bearing radiographs if possible.  This is done to rule out any bony lesions of fractures.  Stress views (discussed in a previous post) may also be performed.  MRI is considered the gold standard for imaging of LCL injuries.  ​​Typically, MRI can demonstrate an LCL failure at its fibular attachment or at the midsubstance of the ligament.  A poor correlation was found in a small study with roughly 30 patients between examination under anesthesia and MRI results for diagnosis of LCL injuries (58 % sensitivity).  This was low compared to ACL injuries (100%) and PLC injuries (87%) [8].  Because these lesions are often found in conjunction with other injuries, it is difficult to determine on physical examination which PLC structure is damaged and the degree of injury to that structure.  When available, ultrasound can be a useful tool in the rapid diagnosis of LCL injuries. Imaging will show a thickened and hypoechoic LCL. A complete tear may show edema, dynamic laxity, or lack of LCL fiber continuity.


Treatment involves both nonoperative and operative management and depends on staging and laxity. Involvement or suspected involvement of additional structures may also alter management. Isolated LCL grade I and II tears are normally managed nonsurgically. Early mobilization has been shown to be helpful [9,10]. Recovery time usually ranges from three to eight weeks and a hinged knee sleeve and early physical therapy are benchmarks of nonoperative treatment.

Isolated grade III LCL injuries have been shown to yield poor results with nonsurgical management in these same studies [9,10]. Conversely, one small cohort of NFL players showed a much faster recovery and equal chance of return to professional play with isolated grade III injuries undergoing nonoperative management [11].

Primary repair is indicated for acute bony avulsions of the femoral or fibular FCL attachment. However, a repair is not recommended for midsubstance tears [12]. Indications for reconstruction include all grade III midsubstance LCL tears and chronic lateral knee instability secondary to FCL injury. More recent evidence has been geared more towards an anatomic technique utilizing a semitendinosus allograft or autograft and has been shown to restore objective knee stability [13,14]. Two separate studies have shown improved subjective and objective outcomes when treating LCL midsubstance tears (Image 3), chronic lateral knee instability and varus stress radiographic gapping of 2.4 to 4.0 mm at 20 degrees flexion [14,15].

LCL Reconstruction

Image 3. LCL reconstruction described (anatomic approach). Adopted from [14].


In summary, lateral collateral ligament injuries in isolation are fairly rare and account for less than 10 percent of knee injuries.  The LCL provides stability of the knee when undergoing varus stress and is stressed and isolated best at 30 degrees.  Injuries to the LCL typically occur with a direct blow to the anteromedial knee and patients normally present with pain laterally and lateral instability.  MRI is the gold standard for imaging but providers should also consider varus stress radiographs.  Treatment depends on grading/staging, which is done by physical examination and MRI.  Grade I and II injuries are normally treated nonoperatively, while grade III injuries have limited studies but are likely best treated with a more anatomic reconstruction.

Case Conclusion

C is the correct answer. The athlete has likely suffered an isolated LCL injury given the current vignette, which is somewhat uncommon. It is very important for the provider to rule out concomitant injuries and the examination does not have any laxity with the Lachman test, valgus stress and no joint effusion is present. Historically, a varus opening of less than 5 mm has signified a low-grade LCL injury, an opening of 6 to 10 mm has signified a moderate grade injury and an opening of more than 10 mm represents a high-grade injury. Grade I injuries are normally treated with early mobilization and physical therapy.
Grawe, Brian, et al. “Lateral collateral ligament injury about the knee: anatomy, evaluation, and management.” JAAOS-Journal of the American Academy of Orthopaedic Surgeons 26.6 (2018): e120-e127.=6l


      1. 1. LaPrade RF, Hamilton CD. The fibular collateral ligament- biceps femoris bursa. An anatomic study. Am J Sports Med. 1997;25(4):439–43

    2. Grawe, Brian, et al. “Lateral collateral ligament injury about the knee: anatomy, evaluation, and management.” JAAOS-Journal of the American Academy of Orthopaedic Surgeons 26.6 (2018): e120-e127.=6l

3. LaPrade RF, Ly TV, Wentorf FA, Engebretsen L. The posterolateral attachments of the knee: a qualitative and quantitative morphologic analysis of the fibular collateral ligament, popliteus tendon, popliteofibular ligament, and lateral gastrocnemius tendon. Am J Sports Med. 2003 Nov-Dec;31(6):854-60.

4. Swenson DM, Collins CL, Best TM, Flanigan DC, Fields SK, Comstock RD. Epidemiology of knee injuries among U.S. high school athletes, 2005/2006-2010/2011. Med Sci Sports Exerc. 2013 Mar;45(3):462-9.
5. Bushnell BD, Bitting SS, Crain JM, Boublik M, Schlegel TF: Treatment of magnetic resonance imaging-documented isolated grade III lateral collateral ligament injuries in National Football League athletes. Am J Sports Med 2010;38(1):86-91.

6. Veltri DM, Deng XH, Torzilli PA, Warren RF, Maynard MJ. The role of the cruciate and posterolateral ligaments in stability of the knee. A biomechanical study. Am J Sports Med. 1995 Jul-Aug;23(4):436-43.

7. Devitt BM, Whelan DB: Physical examination and imaging of the lateral collateral ligament and posterolateral corner of the knee. Sports Med Arthrosc 2015;23(1):10-16.

8. Bonadio MB, Helito CP, Gury LA, Demange MK, Pécora JR, Angelini FJ. Correlation between magnetic resonance imaging and physical exam in assessment of injuries to posterolateral corner of the knee. Acta Ortop Bras. 2014;22(3):124–126. doi: 10.1590/1413-78522014220300928.

9. Krukhaug Y, Mølster A, Rodt A, Strand T: Lateral ligament injuries of the knee. Knee Surg Sports Traumatol Arthrosc 1998;6(1): 21-25.

10. Kannus P: Nonoperative treatment of grade II and III sprains of the lateral ligament compartment of the knee. Am J Sports Med 1989;17(1):83-88.

11. Bushnell, Brandon D., et al. “Treatment of magnetic resonance imaging-documented isolated grade III lateral collateral ligament injuries in National Football League athletes.” The American journal of sports medicine 38.1 (2010): 86-91.

12. Geeslin AG, LaPrade RF (2011) Outcomes of treatment of acute grade-III isolated and combined posterolateral knee injuries: a prospective case series and surgical technique. J Bone Joint Surg Am 93:1672–1683

13. Coobs BR, LaPrade RF, Griffith CJ, Nelson BJ (2007) Biomechanical analysis of an isolated fibular (lateral) collateral ligament reconstruction using an autogenous semitendinosus graft. Am J Sports Med 35(9):1521–1527

14. LaPrade RF, Spiridonov SI, Coobs BR, Ruckert PR, Griffith CJ (2010) Fibular collateral ligament anatomical reconstructions: a prospective outcomes study. Am J Sports Med 38(10):2005–2011

15. Moulton SG, Matheny LM, James EW, LaPrade RF. Outcomes following anatomic fibular (lateral) collateral ligament reconstruction. Knee Surg Sports Traumatol Arthrosc. 2015 Oct;23(10):2960-6

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