Multi-Ligament Knee Dislocation: A Comprehensive Clinical Case Study with Vascular & Neurological Complications

Patient Presentation and History

A 24-year-old semi-professional male football (soccer) player presented to the emergency department following a high-energy, non-contact injury during a match. He describes planting his right foot to change direction rapidly when an opposing player collided with his lateral knee, forcing it into a valgus and hyperextension moment, followed by an audible "pop." He experienced immediate, excruciating pain, gross deformity of the knee, and was unable to bear weight. Paramedics reported the knee was visibly dislocated on arrival at the field, which spontaneously reduced prior to transport. He denies any prior significant knee injuries. His medical history is unremarkable, with no known allergies or comorbidities. He is a non-smoker and denies recreational drug use. His primary concern is return to elite-level sport.

The biomechanics of this specific injury mechanism—a violent valgus force coupled with hyperextension and axial loading—typically results in sequential failure of the capsuloligamentous structures. The medial collateral ligament complex fails first under tension, followed by the anterior cruciate ligament and posterior cruciate ligament as hyperextension progresses, and finally the posterolateral corner as the joint undergoes subluxation and rotational torque. The history of spontaneous reduction is a critical piece of the clinical picture, as it frequently masks the true magnitude of the initial displacement and carries a high correlation with occult popliteal artery traction injuries.

Clinical Examination Findings

Upon arrival, the patient was hemodynamically stable, although in significant pain. The primary survey was negative for concomitant life-threatening or limb-threatening injuries outside the isolated right lower extremity trauma.

Inspection and Palpation

The right knee was significantly swollen with a moderate hemarthrosis, diffuse ecchymosis, and palpable tenderness circumferentially. No obvious skin tenting or open wounds were noted, indicating a closed knee dislocation. The limb was aligned, suggesting spontaneous reduction. The "dimple sign" (invagination of the medial skin into the joint space, indicative of irreducible posterolateral dislocation with medial capsule interposition) was absent. Diffuse tenderness was elicited around the medial and lateral joint lines, the popliteal fossa, and the patellar borders. Palpation of the fibular head revealed localized tenderness, raising suspicion for an avulsion injury of the biceps femoris or fibular collateral ligament.

Range of Motion and Provocative Testing

Active range of motion was severely restricted due to pain, guarding, and massive effusion, limited to an arc of approximately 10 to 40 degrees. Passive range of motion revealed a soft end-feel in both flexion and extension, with gross multidirectional instability. Ligamentous stability testing was performed gently to avoid exacerbating potential neurovascular injury:

• Anterior Cruciate Ligament: The Lachman test revealed a grade III anterior translation (>10mm) with no discernible end-point. The anterior drawer test was also grossly positive. Pivot shift testing was deferred due to the acute nature of the injury and the presence of severe medial and lateral laxity.
• Posterior Cruciate Ligament: A profound posterior sag sign was evident at rest. The posterior drawer test at 90 degrees of flexion demonstrated grade III posterior translation, with the medial tibial plateau stepping off posterior to the medial femoral condyle. The quadriceps active test showed posterior translation that reduced with quadriceps contraction but remained pathologically unstable.
• Medial Collateral Ligament: Valgus stress testing at 0 and 30 degrees of flexion demonstrated grade III laxity (opening >10mm) with no firm endpoint, indicating complete rupture of the superficial medial collateral ligament, the deep medial collateral ligament, and the posterior oblique ligament.
• Posterolateral Corner: Varus stress testing at 0 and 30 degrees of flexion demonstrated grade III laxity. The Dial test, performed in the prone position, showed increased external rotation of the tibia (>15 degrees compared to the contralateral uninjured side) at both 30 and 90 degrees of knee flexion. This confirmed a massive posterolateral corner injury involving the fibular collateral ligament, the popliteus tendon, and the popliteofibular ligament.
• Combined Instabilities: Gross rotational instability was present in both internal and external rotation, consistent with combined bicruciate and bicolumnar disruption, highly suggestive of a multi-ligament knee injury classified as a KD-IV knee dislocation.

Neurological Assessment

Thorough neurological evaluation of the distal extremity is paramount in the setting of multi-ligament knee injuries. Assessment of the common peroneal nerve revealed weakness in dorsiflexion of the ankle and eversion of the foot, graded at 3/5 on the Medical Research Council scale. Extensor hallucis longus function was similarly diminished. Sensory deficit, characterized by decreased response to light touch and pinprick, was present in the first dorsal web space and the anterolateral aspect of the leg. This clinical picture indicated a partial common peroneal nerve palsy, likely secondary to traction neurapraxia or axonotmesis occurring during the initial varus/hyperextension moment that disrupted the posterolateral corner. Tibial nerve function, including plantarflexion, inversion, and plantar sensation, remained entirely intact.

Vascular Assessment

Vascular assessment in knee dislocations must be exhaustive due to the catastrophic consequences of missed popliteal artery injuries. Distal pulses (dorsalis pedis and posterior tibial) were palpable but subjectively diminished compared to the contralateral limb. Capillary refill in the digits was delayed at approximately 3 to 4 seconds, and the distal limb was cool to the touch.

An Ankle-Brachial Index was immediately calculated. The systolic blood pressure of the injured posterior tibial artery was divided by the higher of the two brachial systolic pressures, yielding an Ankle-Brachial Index of 0.85. In the context of knee trauma, an Ankle-Brachial Index of less than 0.90 is a hard clinical sign of vascular compromise and mandates immediate advanced vascular imaging, regardless of the presence of palpable pulses.

Imaging and Diagnostics

Following the clinical assessment, a rapid and protocol-driven diagnostic workup was initiated to define the osseous, ligamentous, and vascular architecture.

Plain Radiography

Initial radiographs included standard anteroposterior, lateral, and oblique views of the right knee. The osseous alignment appeared concentrically reduced on the static films, corroborating the history of spontaneous reduction. However, several subtle radiographic markers of severe ligamentous injury were identified:
* Joint Space Asymmetry: Widening of the medial compartment on the anteroposterior view suggested loss of medial ligamentous integrity.
* Segond Fracture: A small elliptical osseous avulsion was noted adjacent to the lateral tibial plateau, representing an avulsion of the anterolateral ligament complex and highly correlative with anterior cruciate ligament disruption.
* Arcuate Sign: A distinct avulsion fracture of the fibular head styloid process was visualized, representing the insertion of the arcuate ligament complex and confirming structural failure of the posterolateral corner.
* Fibular Head Configuration: No gross dislocation of the proximal tibiofibular joint was observed, though the avulsion fragment indicated the primary site of failure.

Computed Tomography Angiography

Given the diminished pulses and an Ankle-Brachial Index of 0.85, an emergent Computed Tomography Angiography of the bilateral lower extremities with runoff was performed. The imaging revealed a flow-limiting intimal flap in the popliteal artery at the level of the knee joint line, posterior to the tibial plateau. While distal flow was maintained via collateral circulation (explaining the palpable, albeit weak, pulses), the intimal tear represented a significant risk for acute thrombosis and subsequent limb ischemia. No active extravasation or pseudoaneurysm was identified. The popliteal vein appeared patent with no evidence of gross thrombosis, though compressed by the surrounding hematoma.

Magnetic Resonance Imaging

Following stabilization of the vascular injury (detailed in the surgical section), a high-resolution, non-contrast Magnetic Resonance Imaging scan of the knee was obtained to meticulously map the soft tissue disruption for surgical templating.
* Cruciate Ligaments: Complete mid-substance tears of both the anterior cruciate ligament and the posterior cruciate ligament were confirmed. The posterior cruciate ligament was avulsed from its femoral footprint with significant retraction.
* Medial Structures: The superficial medial collateral ligament was avulsed from its tibial insertion, deep to the pes anserinus. The deep medial collateral ligament and posterior oblique ligament were completely disrupted at the joint line.
* Posterolateral Corner: The fibular collateral ligament was torn mid-substance. The popliteus tendon was avulsed from the femoral footprint, and the popliteofibular ligament was completely attenuated.
* Menisci: A complex, displaced bucket-handle tear of the medial meniscus was identified, alongside a radial tear of the lateral meniscus posterior horn root.
* Cartilage and Bone: Extensive bone marrow edema patterns were noted in the lateral femoral condyle and posterolateral tibial plateau, consistent with the pivot-shift mechanism and impaction forces. No full-thickness chondral defects were observed.

Differential Diagnosis

The presentation of a grossly unstable knee following high-energy trauma requires differentiation between purely ligamentous injuries, purely osseous injuries, and combined osseous-ligamentous pathologies.

Surgical Decision Making and Classification

The management of a multi-ligament knee injury, particularly one presenting with vascular compromise, requires a highly coordinated, multidisciplinary approach.

Schenck Classification System

This injury is classified as a Schenck KD-IV knee dislocation (disruption of the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament, and posterolateral corner). The Wascher modification further categorizes this based on the neurovascular status. Given the partial peroneal nerve palsy and the popliteal artery intimal tear, this is a KD-IV-C/N injury. This classification dictates a high-acuity surgical algorithm.

Timing and Staging of Intervention

The definitive management of multi-ligament knee injuries remains a topic of debate regarding early versus delayed reconstruction and single-stage versus multi-stage approaches. However, the presence of a vascular injury dictates an immediate, staged protocol.

Attempting a prolonged, single-stage, four-ligament reconstruction in the acute setting with a freshly repaired popliteal artery poses an unacceptable risk of graft thrombosis, compartment syndrome, and limb loss due to prolonged tourniquet time and extreme joint positioning required during tunnel drilling.

Therefore, the surgical decision-making mandates a two-stage approach:
1. Stage One (Damage Control): Emergent vascular intervention to restore definitive perfusion, coupled with the application of a spanning external fixator to provide rigid skeletal stability, protecting the vascular repair and allowing soft tissue swelling to subside.
2. Stage Two (Definitive Reconstruction): Delayed, single-stage multi-ligament reconstruction and meniscal repair, performed 3 to 4 weeks post-injury once the vascular graft has endothelialized, the capsular structures have sealed, and the patient has regained full passive range of motion.

Surgical Technique and Intervention

Stage One Damage Control and Vascular Repair

The patient was taken emergently to the operating theater. Vascular surgery performed an exploration of the popliteal fossa via a medial approach. The popliteal artery was isolated, and the segment containing the intimal flap was resected. A reversed great saphenous vein interposition graft, harvested from the contralateral extremity to avoid compromising the injured limb's venous return, was utilized to restore arterial continuity.

Following successful revascularization, the orthopedic trauma team applied a rigid, delta-frame spanning external fixator. Half-pins were placed in the anterior femur and the anteromedial tibia, well outside the anticipated zones for future ligamentous tunnel trajectories. The knee was fixed in approximately 15 degrees of flexion to minimize tension on the popliteal artery repair and the posterior neurovascular bundle. Prophylactic four-compartment fasciotomies of the lower leg were performed due to the ischemic time and the risk of reperfusion injury.

Stage Two Definitive Multi Ligament Reconstruction

Three weeks post-injury, the external fixator was removed, and the fasciotomy wounds were successfully closed via delayed primary closure. The patient returned to the operating room for definitive reconstruction.

Patient Positioning and Examination Under Anesthesia
The patient was placed supine on a radiolucent operating table. A lateral post and foot roll were utilized to allow for dynamic positioning and hyperflexion. Examination under anesthesia confirmed persistent grade III laxity in all planes. A non-sterile tourniquet was applied high on the thigh but was not inflated to avoid compromising the vascular graft; hemostasis was maintained via hypotensive anesthesia and meticulous electrocautery.

Graft Selection and Preparation

Given the massive requirement for graft tissue and the desire to minimize donor-site morbidity in an elite athlete, a hybrid allograft/autograft approach was selected:
* Posterior Cruciate Ligament: Achilles tendon allograft with a bone block.
* Anterior Cruciate Ligament: Bone-patellar tendon-bone autograft (harvested from the contralateral knee to preserve extensor mechanism integrity on the injured side).
* Posterolateral Corner: Split Achilles tendon allograft (for the fibular collateral ligament and popliteus tendon reconstruction).
* Medial Collateral Ligament: Semitendinosus allograft.

Tunnel Preparation and Sequence of Fixation

The surgical sequence is critical in multi-ligament reconstruction to ensure appropriate tensioning and avoid tunnel convergence, particularly in the lateral femoral condyle and the proximal tibia.

1. Arthroscopic Meniscal Repair and Cruciate Tunnel Drilling
Standard anterolateral and anteromedial portals were established. The medial meniscus bucket-handle tear was reduced and repaired using an inside-out technique with non-absorbable sutures. The lateral meniscus root tear was repaired via a transtibial pull-out technique.

The posterior cruciate ligament tibial footprint was exposed via a posteromedial portal. A transtibial tunnel was drilled targeting the distal aspect of the posterior cruciate ligament facet to ensure an anatomic trajectory. The femoral tunnel was drilled from outside-in, targeting the anatomic footprint on the medial femoral condyle.

The anterior cruciate ligament tibial tunnel was drilled independently, ensuring a minimum 5mm bone bridge between the anterior cruciate ligament and posterior cruciate ligament tunnels. The femoral tunnel was drilled via an accessory anteromedial portal.

2. Posterolateral Corner Reconstruction (LaPrade Technique)
A lateral hockey-stick incision was made. The common peroneal nerve was identified, neurolysed, and protected. The fibular head and lateral femoral epicondyle were exposed. A tunnel was drilled through the fibular head from anterolateral to posteromedial to reconstruct the popliteofibular ligament. Two femoral tunnels were drilled: one at the fibular collateral ligament footprint (proximal and posterior to the epicondyle) and one at the popliteus footprint (distal and anterior). Meticulous fluoroscopic guidance was used to ensure these tunnels did not converge with the anterior cruciate ligament femoral tunnel.

3. Medial Collateral Ligament Reconstruction
A medial longitudinal incision was utilized. The anatomic footprints of the superficial medial collateral ligament on the medial epicondyle and the tibia (distal to the joint line, deep to the pes anserinus) were identified. Tunnels were drilled for an anatomic reconstruction of the superficial medial collateral ligament and the posterior oblique ligament.

4. Graft Passage and Tensioning Sequence
The sequence of graft fixation is paramount to establishing a central pivot before securing the peripheral stabilizers:
1. Posterior Cruciate Ligament Fixation: The bone block of the Achilles allograft was secured in the femoral tunnel with an interference screw. The graft was passed distally. The knee was cycled, and the posterior cruciate ligament was tensioned and fixed on the tibia at 90 degrees of flexion with an anterior drawer force applied to restore the normal tibiofemoral step-off.
2. Anterior Cruciate Ligament Fixation: The bone-patellar tendon-bone graft was secured in the femur. It was tensioned and fixed in the tibia at full extension.
3. Posterolateral Corner Fixation: The grafts were passed through the fibular and tibial tunnels. The fibular collateral ligament was tensioned at 20 degrees of flexion with a valgus force. The popliteus and popliteofibular ligaments were tensioned at 60 degrees of flexion with neutral rotation.
4. Medial Collateral Ligament Fixation: The medial collateral ligament graft was tensioned at 20 degrees of flexion with a varus force applied to the knee to close the medial joint space.

Following fixation, the knee was taken through a full range of motion. Stability was restored in all planes. The incisions were closed in layers, and the limb was placed in a hinged knee brace locked in full extension.

Post Operative Protocol and Rehabilitation

The rehabilitation following a KD-IV multi-ligament knee reconstruction is arduous, requiring a delicate balance between protecting the healing graft tissue and preventing devastating arthrofibrosis. The protocol must be strictly adhered to, particularly in the context of concurrent vascular repair and meniscal root fixation.

Acute Protection Phase (Weeks 0 to 6)

• Weight Bearing: Strict non-weight bearing for the first 6 weeks to protect the meniscal root repair and the complex articular reconstructions.
• Bracing: The patient is placed in a specialized dynamic posterior cruciate ligament brace (e.g., Jack PCL brace) that applies an anteriorly directed force to the posterior calf, counteracting the posterior subluxation vector of gravity and the hamstrings. The brace is locked in extension for ambulation and sleeping.
• Range of Motion: Passive range of motion is initiated immediately to prevent arthrofibrosis. Flexion is strictly limited to 90 degrees for the first 4 weeks to avoid over-tensioning the posterior cruciate ligament and the meniscal root repairs. Hyperextension is strictly prohibited.
• Muscle Activation: Isometric quadriceps sets and straight leg raises (in the brace) are encouraged. Active hamstring curls are strictly contraindicated for the first 12 weeks to prevent posterior tibial translation and stretching of the posterior cruciate ligament graft.
• Medical Management: Deep vein thrombosis prophylaxis (low molecular weight heparin) is maintained for 4 weeks. Close monitoring of the distal vascular status is performed daily.

Intermediate Rehabilitation Phase (Weeks 6 to 12)

• Weight Bearing: Progressive partial weight bearing is initiated at week 6, advancing to full weight bearing by week 8 to 10, guided by radiographic evidence of tunnel integration and clinical stability.
• Range of Motion: The restriction on flexion is lifted, and the goal is to achieve full symmetrical range of motion by week 10. Gentle active-assisted range of motion is incorporated.
• Strengthening: Closed kinetic chain exercises (e.g., mini-squats, leg press limited to 0-70 degrees) are initiated. Core and hip/gluteal strengthening are emphasized to optimize proximal biomechanics. Open kinetic chain knee extension is avoided to protect the anterior cruciate ligament graft.
• Neurological Monitoring: The peroneal nerve palsy is monitored via serial electromyography (EMG) at 6 and 12 weeks. An ankle-foot orthosis (AFO) is utilized to prevent equinus contracture and assist with gait mechanics while motor function recovers.

Advanced Strengthening and Return to Play (Months 3 to 12+)

• Months 3 to 6: The dynamic posterior cruciate ligament brace is transitioned to a standard functional multi-ligament brace. Proprioceptive training (BOSU ball, balance boards) is aggressively pursued. Light jogging may be initiated around month 5 if adequate quadriceps control (no extension lag) and symmetric range of motion are achieved.
• Months 6 to 9: Sport-specific agility drills, plyometrics, and cutting maneuvers are introduced in a controlled environment. Isokinetic strength testing is performed.
• Return to Play Criteria (Typically 9 to 15 months): Return to elite soccer requires meeting stringent criteria: >90% limb symmetry index on isokinetic quadriceps and hamstring testing, >90% symmetry on a battery of hop tests (single hop, triple hop, crossover hop), normal clinical stability, and psychological readiness. Given the severity of a KD-IV injury, patients must be counseled that return to pre-injury elite levels is challenging and not guaranteed.

Clinical Pearls and Pitfalls

Pearls:
* High Index of Suspicion for Vascular Injury: A spontaneously reduced knee dislocation is a vascular emergency until proven otherwise. Do not rely solely on palpable pulses; an Ankle-Brachial Index <0.90 mandates a Computed Tomography Angiography.
* Staged Approach for Vascular Compromise: Prioritize limb salvage over joint stability. Attempting acute ligament reconstruction in the setting of a fresh vascular repair invites catastrophic complications. Utilize a spanning external fixator for damage control.
* Anatomic Tunnel Placement: Strict adherence to anatomic footprints is essential for restoring normal knee kinematics. Use fluoroscopy liberally during tunnel preparation to avoid convergence, particularly between the anterior cruciate ligament, fibular collateral ligament, and popliteus tunnels in the lateral femoral condyle.
* Fixation Sequence: Always establish the central pivot first. Tension and fix the posterior cruciate ligament to restore the anatomic tibiofemoral step-off before securing the anterior cruciate ligament and peripheral structures.

Pitfalls:
* Missing a Meniscal Root Tear: Failure to identify and repair meniscal root tears during multi-ligament reconstruction leads to rapid joint space narrowing, altered contact mechanics, and premature graft failure.
* Over-tensioning the Posterolateral Corner: Securing the posterolateral corner grafts in excessive internal rotation or excessive flexion can lead to severe postoperative stiffness and a fixed external rotation deficit. Tension at 20-60 degrees of flexion in neutral rotation.
* Neglecting the Peroneal Nerve: Failure to splint the ankle in neutral (via an AFO) in the setting of a peroneal nerve palsy will lead to a fixed equinus contracture, severely complicating the rehabilitation phase regardless of a successful knee reconstruction.
* Inadequate Rehabilitation: Allowing active hamstring contraction too early will inevitably stretch out a posterior cruciate ligament reconstruction. Strict adherence to brace protocols and activity modifications is as critical as the surgical technique itself.