PCL Injury

The posterior cruciate ligament (PCL) is the largest and strongest ligament in the knee, serving as the primary restraint to posterior tibial translation. PCL injuries are less common than ACL injuries but are frequently underdiagnosed. The management of PCL injuries — particularly isolated PCL tears versus combined multiligamentous knee injuries — remains one of the most debated areas in knee surgery, and the vast majority of isolated PCL tears are managed non-operatively.

• PCL anatomy: two functional bundles — anterolateral (AL) bundle: the larger bundle, taut in flexion, primary restraint to posterior translation; posteromedial (PM) bundle: taut in extension; the PCL originates from the medial wall of the intercondylar notch and inserts on the posterior tibial sulcus, approximately 1 cm below the articular surface of the tibia
• The PCL is approximately twice the tensile strength of the ACL; it restrains approximately 95% of posterior tibial translation at 90° of flexion
• Incidence: PCL tears account for approximately 3–20% of all knee ligament injuries; the wide range reflects varying detection rates; isolated PCL tears approximately 40%; combined with other ligamentous injuries approximately 60%
• Most common mechanisms: dashboard injury (posterior force on a flexed knee in a motor vehicle collision — the classic mechanism); hyperflexion with the foot plantarflexed; direct blow to the proximal tibia; hyperextension (usually combined with other injuries); the dashboard mechanism produces isolated or combined PCL tear depending on the force magnitude

• History: motor vehicle accident (dashboard injury); sport injury (fall onto flexed knee with plantarflexed foot); pain and swelling less acute than ACL tear; posterior knee pain; feeling of instability on stairs and downhill activities
• Posterior drawer test: knee at 90° flexion; posterior force on the tibia; positive = posterior tibial translation relative to femur; most sensitive test for PCL tear (sensitivity 90%); graded: Grade I <5 mm (PCL partial), Grade II 5–10 mm (complete PCL), Grade III >10 mm (combined PCL + posterolateral corner or posteromedial corner)
• Posterior sag sign (Godfrey test): with the hip and knee both at 90° flexion, gravity causes the tibia to sag posteriorly in a PCL-deficient knee; the tibial tuberosity appears lower than the contralateral side; positive = PCL-deficient knee; must be compared with the contralateral leg
• Quadriceps active test: knee at 90°; patient actively contracts quadriceps without lifting the heel; in PCL-deficient knee, the tibia (which has sagged posteriorly) is pulled anteriorly by the quadriceps, producing visible anterior tibial shift; positive = PCL-deficient
• Reverse pivot shift: knee taken from 90° flexion to extension with external rotation and valgus; positive = lateral tibial plateau reduces from a posteriorly subluxed position; indicates posterolateral corner (PLC) injury ± PCL; must be distinguished from the standard pivot shift (ACL)
• Assessment of associated injuries: always assess the posterolateral corner (PLC — fibular collateral ligament, popliteus, popliteofibular ligament), posteromedial corner (MCL, POL), ACL, and medial/lateral menisci; combined injuries are common with Grade III PCL tears

• Tibial step-off: normally the medial tibial plateau is approximately 1 cm anterior to the medial femoral condyle when the knee is at 90° flexion; loss of this step-off indicates PCL tear; reversed step-off (tibia posterior to femur) = Grade III = combined injury

• Knee radiographs: AP, lateral, patellar views; assess for avulsion fractures at the PCL tibial insertion (PCL avulsion — treatable with screw fixation); assess for other fractures and bony injury patterns
• Stress radiographs (Telos device or manual): posterior stress at 90° flexion; side-to-side difference >8–12 mm = Grade II–III; quantifies the degree of posterior laxity objectively; useful for grading and surgical decision-making
• MRI knee: gold standard for PCL assessment; shows PCL signal change, tear location, and degree of disruption; also identifies associated injuries (PLC, PMC, menisci, ACL, chondral); PCL avulsion at the tibial insertion is well visualised; both ligament bundles can be assessed
• Knee dislocation workup: if Grade III PCL tear is suspected with multiligamentous injury, formally assess for knee dislocation — CT angiography or vascular duplex of the popliteal vessels; popliteal artery injury occurs in approximately 20–30% of true knee dislocations (ABI <0.9 = perform CT angiography urgently)

The management of PCL injuries depends critically on the grade of injury and whether it is isolated or combined with other ligamentous injuries.

• Isolated Grade I and II PCL tears: non-operative management is the standard of care — the majority of patients (approximately 80–90%) achieve acceptable functional outcomes with rehabilitation; the PCL has better intrinsic healing capacity than the ACL due to better blood supply; rehabilitation focuses on quadriceps strengthening (the quadriceps acts as a dynamic PCL equivalent, pulling the tibia anteriorly); functional PCL brace for high-demand activities
• PCL rehabilitation: early quadriceps strengthening in extension; avoid isolated hamstring curls (hamstrings pull the tibia posteriorly = stress on healing PCL); early weight-bearing and ROM; return to sport at 3–6 months for Grade I–II
• PCL avulsion fracture: PCL avulsion at the tibial insertion (bony avulsion on lateral X-ray) is best treated surgically — screw fixation or suture anchor repair through posterior approach or arthroscopically; restores PCL anatomy; excellent results with anatomical reduction
• Surgical reconstruction for PCL: indicated for Grade III PCL tears (combined multiligamentous injury), acute PCL avulsion bony fractures, failure of non-operative management with ongoing symptomatic instability in high-demand patients
• PCL reconstruction surgical options: single-bundle (AL bundle reconstruction — most common); double-bundle; inlay technique (tibial inlay — avoids the "killer turn" of the transtibial technique); graft choices similar to ACL (BPTB, hamstring, quadriceps, allograft); transtibial technique has a "killer turn" at the posterior tibial cortex which causes graft abrasion — tibial inlay avoids this
• Posterolateral corner (PLC) reconstruction: when combined PCL + PLC injury is present, the PLC must be reconstructed or repaired simultaneously; isolated PCL reconstruction without PLC repair in combined injury leads to failure due to persistent varus and external rotation instability; the popliteofibular ligament and fibular collateral ligament are the key PLC structures to reconstruct

• Knee dislocation (multiligamentous injury): all patients with Grade III PCL tears and combined ligamentous injury should be assessed for formal knee dislocation (even if reduced spontaneously); popliteal artery injury and common peroneal nerve injury are the two critical associated injuries; ABI <0.9 mandates CT angiography; peroneal nerve palsy: assess at presentation and monitor serially; peroneal nerve injury occurs in 15–25% of knee dislocations, most commonly from PLC disruption; recovery is unpredictable
• PLC anatomy and the "fibular-based" reconstruction: the posterolateral corner has three primary structures — the fibular collateral ligament (FCL), the popliteus muscle and tendon, and the popliteofibular ligament; reconstruction uses a figure-of-eight graft around the fibular head to recreate both the FCL and popliteofibular ligament; the Laprade technique is the most widely adopted; must be combined with PCL reconstruction in combined PCL + PLC injury
• Timing of surgery in multiligamentous knee injury: vascular injury takes priority; neurovascular assessment is mandatory before any anaesthesia; ligamentous surgery planned after vascular repair if required; early reconstruction of combined injuries (within 2–3 weeks) gives better results than delayed reconstruction; delayed reconstruction requires more complex surgery and rehabilitation
• Long-term outcomes of PCL deficiency: isolated PCL-deficient knees develop medial compartment and patellofemoral OA at a higher rate than normal knees; approximately 40% develop significant OA at 10 years; quadriceps rehabilitation reduces this risk; patients with Grade III combined injuries and persistent laxity have significantly worse articular outcomes

• PCL: primary restraint to posterior tibial translation; AL bundle primary (taut in flexion); twice the tensile strength of ACL
• Dashboard injury: most common mechanism; posterior force on flexed knee; also hyperflexion with plantarflexed foot
• Posterior drawer test: most sensitive (90%); Grade I <5 mm; II 5–10 mm (flush step-off); III >10 mm (reversed step-off = combined injury)
• Tibial step-off: medial tibia normally 1 cm anterior to medial femoral condyle at 90°; loss = PCL tear; reversed = Grade III combined
• Reverse pivot shift: lateral tibial plateau reduces from posterior subluxation on extension + external rotation + valgus; indicates PLC ± PCL
• Isolated Grade I–II PCL: non-operative standard; 80–90% acceptable outcomes; quadriceps strengthening (avoids hamstring curls); good PCL healing capacity
• PCL avulsion fracture: surgical fixation (screw or anchor); excellent results with anatomical reduction
• Grade III PCL = multiligamentous injury: PLC must be reconstructed simultaneously with PCL; isolated PCL reconstruction fails without PLC repair
• Knee dislocation: popliteal artery injury 20–30%; peroneal nerve injury 15–25%; ABI <0.9 = CT angiography urgently
• Tibial inlay technique: avoids "killer turn" at posterior tibial cortex; reduces graft abrasion compared to transtibial technique