PCL, PLC and multiligament knee injuries

PCL assessment first distinguishes an isolated injury from associated PLC, collateral ligament or ACL injury. A blow to the front of a flexed knee, posterior sag, posterior drawer and anterior movement of the tibia with quadriceps contraction are interpreted together. Posterior sag can make the ACL appear lax, so the tibial starting position is checked before anterior instability is judged.

MRI shows the tear location and associated meniscal or cartilage injury, but apparent ligament continuity does not establish normal functional stability. Posterior stress radiographs are interpreted with the side-to-side difference and imaging conditions documented, alongside pain, gait, instability on stairs and activity demands. Large posterior translation does not necessarily mean a PLC injury; rotational and varus instability require separate assessment.

Initial care for an acute isolated PCL injury can include protection and rehabilitation. The German Knee Society's 2025 consensus supports this initial approach for both partial and complete isolated tears, while much of the supporting evidence remains low level. Treatment decisions consider avulsion fractures, symptomatic instability, activity goals, rehabilitation response and associated lesions rather than a posterior-translation measurement alone.

When reconstruction is considered, reduced posterior translation and recovery of patient-perceived function are documented as separate goals. A benefit from adding PLC reconstruction to an isolated high-grade PCL injury is not assumed. A small retrospective study published in 2025 found no outcome difference between isolated PCL reconstruction and combined PCL–PLC reconstruction, but this does not establish equivalence across all injuries. The surgical scope follows confirmed associated instability and alignment problems.

The PLC includes the fibular collateral ligament, popliteus tendon and popliteofibular ligament, among other posterolateral stabilizers. Varus and external-rotation control can be impaired together, so assessment extends beyond the MRI signal of a single ligament. The injury mechanism, posterolateral pain, common peroneal nerve sensation and motor function, varus thrust and hyperextension during gait are considered together.

The dial test, posterolateral drawer, external rotation recurvatum test and varus stress examination provide complementary information. Knee angle, the tibial starting position and applied force can alter the findings, so conditions are matched for bilateral comparison. Differences in external rotation at 30 and 90 degrees may suggest associated PCL injury; a positive finding at one angle does not establish the injured structures by itself.

Stress radiographs and MRI supplement the direction and magnitude of clinically identified instability. In chronic injuries, bilateral hip-to-ankle radiographs help separate bony varus from lateral joint opening. Missed PLC instability can leave abnormal loading after cruciate reconstruction, so rotational and varus stability are included in the reconstruction plan.

The 2025 international consensus supports reconstruction for confirmed complete grade III PLC injuries and advises against isolated repair of high-grade injuries without augmentation or reconstruction. Repair may be considered for an acute single-structure soft-tissue avulsion after tissue quality and associated injuries are assessed. No reconstruction technique is optimal for every patient; reconstructed structures, nerve protection, tunnel conflicts and rehabilitation restrictions are planned for the actual injury pattern.

A knee dislocation may reduce spontaneously before presentation, leaving apparently normal alignment on imaging. Multiligament injury and neurovascular injury are considered together after high-energy and other injury mechanisms. The deformity at the time of injury, instability, skin and soft-tissue condition, and foot perfusion guide emergency decisions more than the knee's initial appearance.

Foot pulses, skin color and temperature, capillary refill, and common peroneal and tibial nerve sensation and motor function are documented before and after reduction. Palpable pulses alone do not exclude popliteal arterial intimal injury or delayed thrombosis. Signs of ischemia or suspected vascular injury prioritize emergency vascular assessment and the relevant specialist team over ligament MRI.

The 2024 international MLKI consensus recommends a low threshold for CT angiography after high-energy injuries and bicruciate or PLC injury patterns. The 2025 ESVS guideline for extremity trauma does not recommend ABI to diagnose or rule out vascular injury and recommends immediate CTA when significant injury cannot be excluded clinically. An older ABI threshold of 0.9 therefore does not establish that every patient is free of vascular injury.

The sequence of ligament, meniscal and fracture treatment is determined after urgent perfusion and soft-tissue problems are addressed. Early stability is weighed against stiffness risk; open injury, vascular treatment, skin condition and range of motion can alter surgical timing. Consensus favors single-stage reconstruction when possible, but this is not a fixed rule to operate on every injury within the same number of days.

In chronic posterolateral instability, varus alignment can reflect both the static bony shape and dynamic lateral joint opening. The terms primary, double and triple varus help separate these components, but the classification name alone does not determine an osteotomy correction. Hip-to-ankle radiographs, varus stress findings and varus thrust or recurvatum during gait are interpreted within one plan.

Ligament reconstruction alone does not normalize the load-bearing axis. Meaningful residual bony varus can continue to load a reconstruction in varus, so deformity location and lateral ligament laxity are assessed separately. Cartilage and meniscal status, sagittal alignment, and PCL and ACL function are also evaluated to distinguish the causes of pain from the causes of instability.

In selected patients with varus and chronic PLC deficiency, an osteotomy-first strategy followed by reassessment of residual instability can be considered. In a prospective 21-patient study published in 2007, some patients improved sufficiently after osteotomy to avoid additional PLC reconstruction, while multiligament and high-energy injuries more often required reconstruction. This does not mean osteotomy substitutes for reconstruction in every PLC injury.

Posterior tibial slope is considered within sagittal planning, while biomechanical hypotheses are distinguished from clinical outcomes. A 2024 study of PCL reconstruction found no significant differences in patient-reported outcomes or failure rates by slope. Rather than presenting a single slope value as a universal surgical target, the need and timing for further reconstruction are reassessed using coronal and sagittal deformity, remaining ligament function, range of motion and symptoms after osteotomy.