PCL Avulsion Fractures

A PCL tibial avulsion detaches the ligament-bone unit from its posterior tibial insertion. A viable fragment may be reduced and fixed, restoring the native ligament rather than replacing it, but management and outcome depend on fragment geometry, chronicity, associated injury and neurovascular safety.

Mechanism. The classic is the dashboard injury: in a motor vehicle accident the knee strikes the dashboard, driving a posterior force onto the proximal tibia of the flexed knee. The other routes to the same lesion:

• Hyperflexion or direct impact
• High-energy trauma, including multiligament and tibial-plateau injuries
• Paediatric bone-ligament failure patterns

Who. Frequency varies by geography, mechanism and referral population, and the injury is often part of high-energy or multiligament trauma. Age, sex and associated-injury percentages come from small series and should not be treated as universal.

The ligament. The PCL arises from the lateral surface of the medial femoral condyle and inserts in the posterior intercondylar area of the tibia, below the joint surface. Its anterolateral and posteromedial bundles both contribute across flexion. The size and thickness of the avulsed fragment vary, and the attachment may carry periosteal or comminuted extensions.

What lies behind it. The popliteal vessels and tibial nerve lie posterior to the insertion, with the popliteus and posterior capsule intervening. The anterior tibial artery may take a high or aberrant course close to posterior tibial drilling. Direct posterior and posteromedial approaches, guidewires and tibial tunnels all approach the popliteal bundle.

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How it fails. Failure may occur through bone, through the bone-ligament interface or through the ligament itself. With time a fragment may scar, resorb or remain reducible. Fixation aims to restore articular contour, PCL length and tension, and posterior stability, restoring the native insertion without overconstraint and without breaking up the fragment or penetrating posteriorly.

Describe the injury rather than force it into a type. Fragment geometry, displacement and chronicity each inform the treatment, and none of them dictates it on its own.

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History. Expect immediate pain and swelling, inability to bear weight, posterior knee pain and a knee that gives way. The classic mechanism is the dashboard blow described above.

Examination. The knee carries an effusion (haemarthrosis) and is held in slight flexion, and the gait is antalgic. The posterior knee is tender, and both flexion and extension are limited by pain and effusion. Normally the tibia steps off 1 cm anterior to the femoral condyle; PCL injury causes posterior translation, and the step-off becomes abnormal.

The ligament tests.

• Posterior drawer - posterior translation; the most sensitive test. Assess the amount of translation and the quality of the endpoint
• Posterior sag sign - the tibia sags posteriorly
• Quadriceps active test - the tibia reduces with quadriceps contraction
• Dial test - may be positive if the PLC is injured

Associated injuries. Reported rates are 20-30% for posterolateral corner injury, 10-15% for ACL injury and 10-20% for meniscal tears, figures to hold with the caution above. Bone bruises of the anterior tibia and anterior femur form a kissing-contusion pattern.

Radiographs. AP and lateral views of the knee. The lateral is the critical view: it shows the fragment on the posterior tibia, its size and its posterior displacement, and an abnormal posterior tibial step-off. Look also for associated tibial plateau and femoral condyle fractures.

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CT. Essential for surgical planning. It measures fragment size and displacement, shows comminution and associated fractures, and plans the fixation strategy. Three-dimensional reconstruction helps with complex comminution, fragment rotation and preoperative planning.

MRI. Not routine, but indicated if associated injuries are suspected: PLC, ACL and meniscal tears and cartilage injury. It also shows the PCL fibres, which are usually intact and attached to the fragment, and the fragment's relation to the tibia.

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The posterior tibial fragment is the diagnostic lesion, but two secondary avulsion signs on plain films flag the concomitant injuries that change the operation. Both are easily confused with the classic (lateral, ACL-associated) Segond fracture listed in the differential above, so they are worth learning as a set.

Reverse Segond fracture. A small cortical avulsion off the medial tibial plateau margin, at the attachment of the deep medial collateral ligament and medial capsule: the mirror image of the classic lateral Segond fleck. It is strongly associated with PCL injury and a medial meniscus tear, whereas the lateral Segond signals ACL injury. The mechanism is valgus with external rotation, distinct from the dashboard mechanism of the isolated PCL fragment but often part of the same high-energy event. A medial-margin fleck on the AP film should trigger a deliberate search for the posterior tibial avulsion and MRI assessment of the medial meniscus.

Arcuate (fibular styloid) sign. An avulsion fleck off the fibular styloid, at the arcuate-complex insertion, signals a posterolateral corner injury, which co-exists with PCL injury in a meaningful minority of cases. Full PLC evaluation and reconstruction belong to the dedicated posterolateral-corner-injuries topic. The point here is that a tiny fibular-head fleck alongside a posterior tibial fragment means this is not an isolated PCL avulsion, and combined instability must be looked for.

Assess first. Determine fragment size, displacement and timing, look for associated PLC, ACL and meniscal injury, and plan the approach. A combined injury, whether PLC, ACL, meniscus, plateau or vascular, is treated as a whole knee in a planned sequence.

Non-operative treatment. Rarely indicated: minimal displacement (under 2 mm), a low-demand patient, or a medical contraindication to surgery. Outcomes are poor compared with surgical fixation, and the usual result is persistent instability. The protocol:

• Extension brace for 6-8 weeks
• Non-weight-bearing initially
• Progressive weight bearing and range of motion
• Quadriceps strengthening

Operative indications. The 2 mm figure used here is conventional rather than validated (see Classification).

• Absolute: displacement over 2 mm, symptomatic instability, a high-demand patient
• Relative: minimal displacement with symptoms, associated injuries requiring surgery

Timing. Early fixation, within about 3 weeks, is conventional, and a fragment presenting beyond about 6 weeks may need reconstruction instead. No cited series quantifies either cut-off.

Screw or suture. Size is often quoted as the dividing line: a screw for a single fragment over 1 cm in good bone, suture anchors for one under 1 cm, comminuted or in poor bone. It is not a universal cut-off. A small or thin fragment may split or be penetrated by a screw, and fragment thickness, comminution, bone quality and PCL attachment decide between screw, suture, bridge or hybrid fixation.

Posterior ApproachScrew FixationSuture Anchor Fixation

Positioning. Prone on a standard operating table, with a thigh tourniquet (which may be deflated for exposure), the contralateral leg abducted and the image intensifier in position.

Incision. A posterior midline or posteromedial incision of 8-10 cm, raising full-thickness flaps. The named approaches and the safe interval are set out in the next section.

Exposure. With the popliteal artery and tibial nerve identified and protected (see the alert below), retract the bundle medially or laterally, then expose the posterior tibia and the avulsed fragment.

Technique.

• Reduce the fragment to its tibial bed
• Provisional K-wire fixation
• Guidewire through the centre of the fragment
• Cannulated, partially threaded screw, 3.5-4.5 mm
• Countersink if needed
• Confirm reduction and stability

Trade-off. A screw gives compression across the fracture and strong, stable fixation with a familiar technique. It needs a fragment large enough to take it, and it may be prominent if not countersunk.

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Technique.

• Reduce the fragment to its tibial bed
• Prepare the bed, debriding to bleeding bone
• Place 2-3 suture anchors in the tibial bed
• Pass the sutures through the PCL and fragment
• Tie them to secure the fragment
• Confirm reduction and stability

Trade-off. Anchors suit small or comminuted fragments, leave no prominent hardware and are flexible in use. They compress less than a screw and may need more anchors.

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Arthroscopic fixation. Open and arthroscopic routes both work in selected hands, and posteromedial, direct posterior or arthroscopic access is chosen according to the fragment and the surgeon's expertise. Arthroscopic tunnels carry their own neurovascular risk, distinct from that of the open approaches, so vessel variants and a safe trajectory are defined before drilling.

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The guidelines table below names the "Burks / Trickey" open posterior approach, but the operative point examiners are really testing is how the popliteal neurovascular bundle is kept out of harm's way. That is a matter of which interval you choose, not just where the skin incision runs.

The approaches by name.

• Trickey posterior (midline). A lazy-S popliteal incision giving direct access to the posterior capsule. Because it crosses the popliteal fossa it requires formal identification and mobilisation of the popliteal vessels and tibial nerve, so it is generally reserved for combined injuries needing wide exposure.
• Burks–Schaffer posteromedial. A more medial incision that uses the interval between the medial head of gastrocnemius and semimembranosus, avoiding the midline popliteal dissection.
• Lobenhoffer / posteromedial inverted-L. A widely used modern variant giving the same posteromedial window onto the PCL facet of the posterior tibia.

The safe interval. The posteromedial approaches share one protective manoeuvre: develop the plane medial to the medial head of gastrocnemius, then retract that muscle belly laterally. The retracted muscle then sits as a muscular shield between the operative field and the popliteal artery, vein and tibial nerve, so the fragment can be reduced and fixed without dissecting directly onto the vessels. That is why a posteromedial route is generally preferred over a midline popliteal dissection for the isolated tibial avulsion.

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The killer curve is not a concern here: this is an avulsion fixation, not a reconstruction.

Neurovascular injury. Direct injury adds to the causes in the table, and avoiding excessive retraction to the prevention. An arterial injury needs immediate vascular surgical consultation.

Nonunion. Devascularisation of the fragment adds to inadequate fixation and poor reduction, and proper timing joins secure fixation and good apposition in prevention. Management is revision fixation, with bone graft if needed.

Residual laxity. Fragment resorption is a further cause. The laxity is usually asymptomatic and does not affect function; if it is symptomatic, revise the fixation, or reconstruct the PCL if needed.

Stiffness. The table gives 5-10%, with prolonged immobilisation as the risk factor and early motion at 2-4 weeks as the prevention. In the Hooper systematic review arthrofibrosis was the commonest complication after both open and arthroscopic fixation, reported at up to 35% arthroscopic and up to 25% open. Those ranges span zero, so the primary studies disagree rather than give a usable rate.

The knee is kept in a hinged brace locked in extension for 4-6 weeks, non-weight-bearing for the first 4-6 weeks, with passive motion through the unlocked brace from 2-4 weeks. Quadriceps sets and straight-leg raises start immediately.

• Weeks 0-2 - brace locked in extension, non-weight-bearing, quadriceps sets and straight-leg raises, ice and elevation
• Weeks 2-4 - brace unlocked for passive motion 0-90 degrees, still non-weight-bearing, stationary bike when range allows, quadriceps strengthening
• Weeks 4-6 - progressive weight bearing from partial to full, full passive range, quadriceps strengthening, balance and proprioception
• Weeks 6-12 - full weight bearing, progressive strengthening and sport-specific training, working towards the return-to-sport criteria below

After fixation. Union is the rule in the cited series, with mean Lysholm scores of 93-95, though no verified percentage exists. 80-85% return to their pre-injury level, and complications (nonunion, residual laxity, stiffness) run at 10-15%.

By timing. Early fixation gives the results above. Subacute fixation at 3-6 weeks gives 75-85% good results. Chronic cases beyond 6 weeks may need reconstruction, and their outcome is less predictable, with no verified success rate.

What predicts the result. Early fixation (within 3 weeks), anatomic reduction, secure fixation and complete rehabilitation favour a good outcome. Delayed fixation (over 6 weeks), malreduction, inadequate fixation and incomplete rehabilitation count against it.

Arthritis. The risk is low with proper treatment, under 5% at 10 years, and higher with malreduction or persistent instability. Proper reduction and fixation minimise it.

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Prevention. Seatbelt use prevents the dashboard injury; airbag deployment, safe driving and protective equipment in sport do the rest of the primary work. After injury, the secondary measures are complete rehabilitation before return to sport, continued strength and conditioning, and a gradual return to activity.

Return to sport. Usually at 6-9 months after surgery, depending on the sport and level. Age, sport level, rehabilitation compliance and timing of fixation all affect it. The criteria:

• Full range of motion, equal to the other knee
• Quadriceps strength over 90% of the contralateral side
• No effusion
• No instability, with a negative posterior drawer
• Single-leg hop over 90% of the contralateral side
• Agility testing passed and sport-specific drills completed

Global Epidemiology

• PCL injuries account for roughly 3-20% of acute knee ligament injuries; isolated bony tibial avulsions are a small subset.
• In pooled series, motor vehicle and motorcycle trauma cause the majority of tibial-sided avulsions (around 68% in the largest systematic review, with motorcycle crashes dominant in many Asian cohorts).
• High-energy mechanisms drive a male predominance and a 20-40 year peak. In limited-resource and high-motorcycle-density regions the absolute burden is higher.

Side-by-Side Guidance

There is no high-level guideline mandating a single technique. Consensus across societies is: displaced fragments should be reduced and stably fixed, repair is preferred over reconstruction when a fixable fragment exists, and concomitant ligament/meniscal injury must be addressed.

Registry & Resource Notes

• No dedicated arthroplasty-style registry tracks PCL avulsion fixation; evidence is limited to Level II RCTs and Level IV series/systematic reviews.
• High-resource settings: increasing use of arthroscopic suture-button/suture-bridge fixation to avoid open popliteal dissection, despite longer operative time and higher cost (Sundararajan RCT).
• Limited-resource settings: open posterior screw or staple fixation remains the workhorse - faster, cheaper, and not dependent on advanced arthroscopic instrumentation.

Related pages: PCL Injuries for the midsubstance ligamentous tear this must be separated from - the whole reason a bony avulsion is worth identifying is that it can be repaired rather than reconstructed; Posterolateral Corner Injuries for the combined pattern that turns an isolated PCL problem into a rotational one and changes the operation, and for the dial test that detects it; Knee Dislocation Management for the multiligament context in which many of these fragments are found, and the vascular assessment it mandates; Vascular Injury in Fracture-Dislocation for the popliteal artery that governs every posterior approach here; Tibial Spine Fractures for the exact mirror injury at the other cruciate insertion, where the same repair-not-reconstruct logic applies; Tibial Plateau Fractures for the posteromedial approaches and fragment-specific fixation this shares; Physeal Injuries and the Salter-Harris Classification for the immature knee, in which the equivalent injury takes the physis rather than the ligament; and ACL Injuries for the contrasting cruciate, where midsubstance rupture is the rule and avulsion the exception.