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 particularly posterolateral corner (PLC) injury 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 2-3 mm thick 4-5 mm wide 66 mm length origin posterior (3.1 mm) and proximal (1.4 mm) to lateral epicondyle posterior and proximal to origin of popliteus popliteus origin is 18.5 mm from LCL origin insertion anterolateral fibula head covers 38% of the fibular width most anterior structure on proximal fibula order of insertion from anterior to posterior LCL → popliteofibular ligament → biceps femoris Blood supply anterior tibial recurrent arteries and inferolateral geniculate arteries Biomechanics function primary restraint to varus stress at 5° and 30° of knee flexion provides 55% of restraint at 5° provides 69% of restraint at 30° 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 entire length of ligament can be palpated by placing patient in figure-of-4 position intact ligament will be a palpable cordlike structure motion hyperextension or varus (lateral) thrust gait neurovascular exam common peroneal nerve injuries may occur with LCL/PLC injury provocative tests varus stress test varus instability at 30° flexion only - isolated LCL injury varus instability at 0° and 30° flexion - combined LCL +/- ACL/PCL injuries dial test increased tibial external rotation (> 10° compared to contralateral side) at 30° knee flexion combined LCL and posterolateral corner injuries 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 correlate with LCL/PLC injury due to a hyperextension-varus mechanism 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 isolated grade I or II LCL injury (no instability at 0°) outcomes return to sport expected in 6-8 weeks progressive varus/hyperextension laxity can occur with unrecognized associated injuries to the PLC Operative isolated LCL repair indications isolated acute (< 2 weeks) grade III LCL injury with avulsed ligament from anatomic attachment site (i.e fibula) outcomes some studies have shown failure rates as high as 40% with repair isolated LCL reconstruction indications subacute/chronic (> 2 weeks) grade III LCL injury with persistent varus instability complete mid-substance acute grade III LCL injury with persistent varus instability outcomes studies shown consistently better outcomes compared to LCL repair 6% failure rate at 3 year followup best results noted with anatomic reconstruction using a semitendinosus autograft LCL + PLC reconstruction indications rotatory instability involving LCL/PLC posterolateral instability (LCL/PLC) outcomes more favorable outcomes when surgeries are done acutely after injury 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 uses the interval between iliotibial band (superior gluteal nerve) and biceps femoris (sciatic nerve) incise the fascia between ITB and biceps to expose the LCL insertion on the fibular head, if needed develop a second interval proximally within ITB to identify the insertion on lateral femoral epicondyle, if needed neurolysis of peroneal nerve should be performed 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 semitendinosus autograft, patellar tendon allograft, achilles tendon allograft semitendinosus autograft is preferred graft for LCL reconstruction since LCL is ~70 mm, semitendinosis provides a closer anatomical size as compared to other grafts ~50 mm is size of patellar tendon autograft semiteninosus stronger than gracilis and less chance of saphenous nerve irritation during harvest anatomic reconstruction fibular tunnel drill from lateral aspect of fibula head towards the posteromedial asepct of fibular styloid, just distal to popliteofibular ligament lateral femoral condyle tunnel starting point just posterior to lateral epidconyle (~ 3 mm) exiting anteromedially complications donor site morbidity semitendinosus and gracillus autograft saphenous nerve neuropraxia MCL injury LCL + PLC reconstruction approach lateral approach to the knee as detailed above techniques fibular-based reconstruction (Larson technique) for LCL and popliteofibular ligament reconstruction hamstring graft passed through bone tunnel in fibular head limbs crossed to create figure-of-eight which is then fixed to lateral femur transtibial double-bundle reconstruction of LCL and popliteofibular ligament split Achilles tendon is fixed to the isometric point of the femoral epicondyle one limb is fixed to the fibular head with a bone tunnel and transosseous sutures to reconstruct the LCL second limb is brought through the posterior tibia to reconstruct the popliteofibular ligament 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