Summary Lateral Collateral Ligament (LCL) injuries of the knee typically occur due to a sudden varus force to the knee and often present in combination with other ipsilateral ligamentous knee injuries (ie. PLC, ACL). Diagnosis can be suspected with increased varus laxity on physical exam but require MRI for confirmation. Treatment can be nonoperative or operative depending on the severity of injury to the LCL as well concomitant injuries to surrounding structures and ligaments in the knee. Epidemiology Incidence isolated injury extremely rare (< 2% knee injuries) 7-16% of all knee ligament injuries when combined with concurrent injuries login to view 1 more bullet Demographics isolated LCL injuries are most commonly seen in gymnasts and tennis players Etiology Pathophysiology traumatic direct blow or force to the medial side of the knee excessive varus stress, external tibial rotation, and/or hyperextension Associated conditions injuries to other components of PLC ACL injuries PCL injuries Anatomy LCL characteristics tubular, cordlike structure dimensions login to view 3 more bullets origin posterior (3.1 mm) and proximal (1.4 mm) to lateral epicondyle posterior and proximal to origin of popliteus login to view 1 more bullet insertion anterolateral fibula head login to view 1 more bullet most anterior structure on proximal fibula login to view 2 more bullets Blood supply anterior tibial recurrent arteries and inferolateral geniculate arteries Biomechanics function primary restraint to varus stress at 5° and 30° of knee flexion login to view 2 more bullets secondary restraint to posterolateral rotation with <50° flexion resists varus in full extension along with ACL and PCL located behind the axis of knee rotation tight in extension and lax in flexion tensile strength: 750 N (valgus) Classification LCL tear classification (based on lateral joint opening compared to contralateral side) Grade 1 0-5 mm lateral joint opening Grade 2 6-10 mm lateral joint opening Grade 3 > 10 mm lateral joint opening without a firm endpoint LCL tear MRI classification Grade 1 Subcutaneous fluid surrounding the midsubstance of the ligament at one or both insertions Grade 2 Partial tearing of ligament fibers at either the midsubstance or one of the insertions Grade 3 Complete tearing of ligament fibers at either the midsubstance or one of the insertions Presentation Symptoms common symptoms instability near full knee extension difficulty ascending and descending stairs difficulty with cutting or pivoting activities lateral joint line pain and swelling Physical exam inspection ecchymosis and lateral joint soft tissue swelling palpation tenderness over LCL insertion login to view 2 more bullets motion hyperextension or varus (lateral) thrust gait neurovascular exam common peroneal nerve injuries may occur with LCL/PLC injury provocative tests varus stress test login to view 2 more bullets dial test login to view 2 more bullets Imaging Radiographs recommended views weightbearing AP, lateral, and varus stress radiographs findings may show asymmetric lateral joint line widening MRI indications imaging modality of choice to grade severity and location of LCL injury findings most tears are noted off of fibular insertion medial compartment bony contusions on T2-weighted images login to view 1 more bullet sensitivity 95% sensitivity much higher senstivity than exam under anesthesia (58%) since lesions are often difficult to isolate on examination alone Treatment Nonoperative limited immobilization, progressive ROM, and functional rehabilitation indications login to view 1 more bullet outcomes login to view 2 more bullets Operative isolated LCL repair indications login to view 1 more bullet outcomes login to view 1 more bullet isolated LCL reconstruction indications login to view 2 more bullets outcomes login to view 3 more bullets LCL + PLC reconstruction indications login to view 2 more bullets outcomes login to view 1 more bullet Techniques Limited immobilization, progressive ROM, and functional rehabilitation progressive ROM of the knee with subsequent emphasis on quadriceps and hamstring strenghthening early studies showed treatment with 6 weeks of casting effective at healing led to signficant knee stiffness Isolated LCL repair approach lateral approach to the knee login to view 4 more bullets techniques traction suture should be placed in ligament to determine if repair is possible (with knee in extension) suture anchors for repair of avulsed ligament to femur or fibula Isolated LCL reconstruction approach lateral approach to knee as detailed above technique commonly used grafts login to view 5 more bullets anatomic reconstruction login to view 4 more bullets complications login to view 4 more bullets LCL + PLC reconstruction approach lateral approach to the knee as detailed above techniques fibular-based reconstruction (Larson technique) for LCL and popliteofibular ligament reconstruction login to view 2 more bullets transtibial double-bundle reconstruction of LCL and popliteofibular ligament login to view 3 more bullets anatomic reconstruction of multiple injured structures (LCL, popliteus tendon, and popliteofibular ligament) using bifid graft (split Achilles tendon) Complications Persistent varus or hyperextension laxity risk factors type III injuries managed non-operatively missed concomitant PCL or PLC injury Peroneal nerve injury incidence occurs in up to 44% of multi-ligamentous injuries that involve the LCL/PLC Stiffness risk factors prolonged immobilization following nonoperative management Physeal arrest risk factors errant lateral condylar LCL fixation during reconstruction in skeletally immature patient Prognosis LCL healing can be unreliable and depends on degree of injury studies show that the LCL does not heal as well as the MCL