Orthopaedic Surgery - Posterior Cruciate Ligament Injury

Basics

Posterior cruciate ligament (PCL) injury involves disruption of the ligament that serves as the primary restraint to:

Posterior translation of the tibia relative to the femur.

The PCL also contributes to:

Rotational stability

and overall stability of the knee, particularly at higher degrees of flexion.

Classification

PCL injuries are commonly graded according to the amount of posterior tibial translation observed during the:

Posterior drawer test.

Grade I

The tibial plateau remains:

Anterior to the femoral condyles

despite increased posterior translation.

This generally represents a:

Partial or lower-grade injury.

Grade II

The anterior surface of the tibial plateau becomes approximately:

Level with the femoral condyles.

This reflects greater posterior laxity.

Grade III

The tibial plateau translates:

Posterior to the femoral condyles.

A grade III injury suggests major PCL insufficiency and should raise concern for associated injury to structures such as the:

Posterolateral corner

or other knee ligaments.

Epidemiology

PCL injuries occur most commonly in:

Young active adults.

Historically, males have been affected more frequently than females, reflecting greater exposure to:

Collision sports

and

High-energy trauma.

Associated Ligament Injuries

PCL tears frequently occur together with other knee injuries rather than in isolation.

Associated injuries may involve the:

Anterior cruciate ligament

Medial collateral ligament

Posterolateral corner

Menisci

Articular cartilage

Common Causes

Typical settings include:

Sports-related trauma

and

Motor vehicle collisions.

Incidence

PCL injury is substantially less common than:

ACL injury

and is relatively uncommon outside athletic or high-energy traumatic settings.

Risk Factors

Important risk factors include:

Motor vehicle collision

Collision sports

Direct anterior tibial trauma

Knee hyperflexion

Hyperextension injury

Genetics

There is no recognized Mendelian inheritance pattern for traumatic PCL injury.

Etiology

The classic mechanism is a:

Direct blow to the anterior proximal tibia while the knee is flexed.

This forces the tibia:

Posteriorly relative to the femur.

Dashboard Injury

A classic example occurs during a motor vehicle collision when the flexed knee strikes the:

Dashboard.

The resulting posteriorly directed force on the tibia can rupture the PCL.

Sports Mechanism

In sports, injury may occur when an athlete falls onto a:

Flexed knee with the foot plantarflexed.

The tibial tubercle or anterior proximal tibia strikes the ground and drives the tibia posteriorly.

Hyperflexion

PCL rupture can also occur through:

Extreme knee flexion

without a direct blow.

This mechanism may tension the ligament beyond its structural capacity.

Hyperextension

Severe:

Knee hyperextension

may injure the PCL, often together with other capsuloligamentous structures.

Associated Conditions

High-energy PCL injuries may be associated with:

Knee dislocation

and potentially:

Popliteal artery injury.

Because vascular compromise can threaten the limb, neurovascular examination is essential.

Diagnosis

Diagnosis is based on:

Mechanism of injury

Physical examination

and

Imaging.

Signs and Symptoms

Acute symptoms may include:

Knee pain

Swelling

Posterior knee discomfort

Mild to moderate effusion

Absence of a Pop

Unlike many ACL injuries, patients with an isolated PCL tear may not report:

An audible or subjective pop.

Symptoms can initially be less dramatic.

Instability Symptoms

Patients may describe:

Vague unsteadiness

Difficulty with deceleration

Discomfort during loaded knee flexion

rather than obvious recurrent instability.

Chronic PCL Injury

Patients with chronic PCL insufficiency may report:

Anterior knee pain

Posterior knee discomfort

Pain when descending stairs

Pain during deceleration

Giving-way sensations

Anterior Knee Pain

Chronic posterior tibial translation changes knee mechanics and increases loading of the:

Patellofemoral joint

and

Medial compartment.

This can explain anterior or medial knee pain despite the ligament injury being posterior.

Genu Recurvatum

Longstanding combined instability may occasionally produce:

Knee recurvatum

or hyperextension deformity.

This is more suggestive of a broader multiligament injury than an isolated low-grade PCL tear.

Physical Examination

A complete knee and neurovascular examination should be performed.

Neurovascular Examination

Assess:

Distal pulses

Capillary refill

Motor function

Sensation

Particular attention is required after:

High-energy trauma

or suspected:

Knee dislocation.

Posterior Drawer Test

The posterior drawer test is the primary examination maneuver for PCL integrity.

Position the patient:

Supine

with the hip flexed and knee at approximately:

90° of flexion.

The foot is stabilized while the examiner applies:

Posterior force to the proximal tibia.

Posterior Drawer Interpretation

Assess:

Amount of posterior translation

and

Quality of the endpoint.

The injured knee should be compared with the:

Contralateral side.

Excessive posterior translation indicates:

PCL insufficiency.

Posterior Sag Sign

The posterior sag sign evaluates resting posterior displacement of the tibia.

With the patient supine and the:

Hips flexed

Knees flexed approximately 90°

the affected tibia may visibly:

Sag posteriorly relative to the femur.

Loss of the normal anterior tibial step-off supports the diagnosis of:

PCL deficiency.

Quadriceps Active Test

The maneuver in which the patient actively attempts to slide the foot forward while the knee is flexed is more accurately termed the:

Quadriceps active test.

With a PCL-deficient knee, quadriceps contraction pulls the posteriorly subluxated tibia:

Anteriorly.

Visible anterior translation supports the diagnosis.

Lachman Test

The Lachman test should be performed to assess for associated:

ACL injury.

It evaluates anterior tibial translation with the knee flexed approximately:

20–30°.

Varus and Valgus Stress Testing

Collateral ligament stability should be assessed using:

Varus stress

and

Valgus stress.

Posterolateral Corner Evaluation

Grade III PCL laxity should prompt careful assessment of the:

Posterolateral corner.

Tests may include:

Dial test

Varus stress examination

Posterolateral drawer testing

depending on the clinical setting.

Laboratory Tests

No laboratory tests are routinely required for an uncomplicated PCL injury.

Imaging

Plain Radiographs

Initial radiographs generally include:

AP

and

Lateral knee views.

They are useful for identifying:

Associated fractures

Posterior tibial avulsion fracture

Other traumatic abnormalities.

Tibial Avulsion Fracture

The PCL may avulse a fragment from its insertion on the:

Posterior proximal tibia.

This is more readily seen on:

Lateral radiographs

and may alter management.

Stress Radiography

Posterior stress radiographs can objectively quantify:

Posterior tibial translation.

They are especially useful in:

Chronic injury

Surgical planning

Grading severe laxity

MRI

MRI is highly sensitive for identifying:

PCL rupture

and associated injuries involving:

ACL

Menisci

Collateral ligaments

Posterolateral corner

Articular cartilage

Acute Versus Chronic MRI

Acute PCL tears are usually readily visible on MRI.

Chronic PCL injuries can occasionally appear:

Continuous or partially healed on MRI

despite persistent functional laxity.

Therefore, chronic diagnosis should rely on:

Clinical examination and objective laxity, not MRI alone.

Pathological Findings

The PCL may fail through:

Midsubstance rupture

Proximal avulsion

Distal avulsion

or

Bony avulsion from the tibial insertion.

Differential Diagnosis

Important alternatives or associated injuries include:

ACL injury

Tibial plateau fracture

Meniscal tear

Posterolateral corner injury

Multiligament knee injury

Treatment

General Principles

Many isolated PCL tears can initially be treated:

Nonoperatively.

Treatment decisions depend on:

Injury grade

Associated ligament injury

Symptoms

Functional demands

Chronicity

Initial Stabilization

Early treatment may include:

Crutches

Knee immobilizer or brace

Ice

Activity modification

Pain control

Weight Bearing

Patients with isolated injuries may generally progress with:

Protected or partial weight bearing as tolerated

depending on pain and associated injuries.

Early Motion

Once acute symptoms permit, treatment emphasizes:

Early controlled range of motion

and

Muscle strengthening.

Prolonged unnecessary immobilization should be avoided.

Bracing

A brace may be used to reduce posterior tibial sag during healing.

Modern PCL-specific dynamic braces may provide anteriorly directed support to the tibia.

The benefit of routine bracing varies according to:

Injury severity

and

Rehabilitation protocol.

Physical Therapy

Rehabilitation is the cornerstone of nonoperative treatment.

A PCL-specific program emphasizes:

Quadriceps strengthening

Hip and core strengthening

Controlled range of motion

Proprioception

Gradual return to functional activity

Quadriceps Strengthening

The quadriceps help translate the tibia:

Anteriorly

and therefore act as a dynamic stabilizer in a PCL-deficient knee.

Quadriceps rehabilitation is particularly important.

Hamstring Loading

Early aggressive hamstring strengthening is generally avoided because hamstring contraction can:

Pull the tibia posteriorly

and increase stress on the healing PCL.

Hamstring loading is typically introduced progressively later in rehabilitation.

Range of Motion

Early flexion may be limited or controlled according to the:

Severity of injury

Healing phase

and

Associated injuries.

The goal is to restore motion without allowing excessive posterior tibial translation.

Medication

First Line

Pain may be treated with:

NSAIDs

or

Acetaminophen, when appropriate.

Severe Acute Pain

Short-term opioid medication is rarely required but may occasionally be used for:

Severe acute traumatic pain

or

Postoperative pain.

Surgery

Surgery is not required for most isolated low-grade PCL injuries.

Relative Surgical Indications

Operative treatment may be considered for:

Symptomatic grade III PCL injury

Combined posterolateral corner injury

Multiligament knee injury

Associated repairable meniscal or articular injury

Persistent instability or giving way

Activity-related pain despite rehabilitation

Progressive symptomatic degenerative change

Avulsion Fracture

A significantly displaced PCL bony avulsion may be treated with:

Reduction and internal fixation.

Fixation restores the native ligament attachment when the fragment is repairable.

PCL Reconstruction

Ligament reconstruction is generally reserved for patients with:

Persistent symptomatic instability

or

Pain and functional limitation despite appropriate rehabilitation.

Graft Options

Reconstruction may use:

Autograft

or

Allograft.

Arthroscopically Assisted Reconstruction

Modern PCL reconstruction is usually performed with:

Arthroscopic assistance.

These procedures are technically demanding because of the:

Deep posterior tibial insertion

and nearby:

Neurovascular structures.

Reconstruction Techniques

Techniques include:

Transtibial single-bundle reconstruction

Tibial inlay single-bundle reconstruction

Transtibial double-bundle reconstruction

Tibial inlay double-bundle reconstruction

Single- Versus Double-Bundle Reconstruction

The PCL contains functionally important:

Anterolateral

and

Posteromedial bundles.

Single- and double-bundle techniques attempt to restore these stabilizing functions to differing degrees.

The optimal approach depends on:

Surgeon experience

Anatomy

Associated injuries

Multiligament Injury

When PCL injury occurs with:

ACL

MCL

LCL

or

Posterolateral corner injury

the reconstruction strategy must address the entire pattern of instability.

Failure to recognize associated posterolateral instability can lead to:

Persistent laxity

and

Failure of PCL reconstruction.

Follow-Up

Clinical follow-up assesses:

Range of motion

Quadriceps strength

Posterior laxity

Pain

Functional stability

Return to Activity

Return to sport should be based on restoration of:

Full or near-full motion

Adequate quadriceps strength

Functional control

Absence of symptomatic instability

rather than a fixed time point alone.

Prognosis

The prognosis for many isolated PCL injuries is:

Good to excellent.

Most low- and moderate-grade isolated injuries can be treated successfully without surgery.

Chronic Natural History

Some patients tolerate chronic PCL laxity surprisingly well.

However, altered knee biomechanics can gradually increase load in the:

Medial compartment

and

Patellofemoral joint.

Complications

Recurrent Instability

Persistent PCL deficiency may lead to:

Giving way

Difficulty with deceleration

Reduced athletic confidence

Reconstruction Failure

Potential causes include:

Graft failure

Tunnel malposition

Unrecognized associated ligament injury

Poor rehabilitation

Osteoarthritis

Chronic PCL insufficiency may contribute to progressive degeneration, particularly involving the:

Medial compartment

followed by the:

Patellofemoral compartment.

Stiffness

Postoperative or post-traumatic stiffness may occur, particularly after:

Multiligament reconstruction

or prolonged immobilization.

Neurovascular Complications

Because of the PCL’s proximity to the posterior neurovascular structures, operative reconstruction carries a small but important risk of:

Vascular or nerve injury.

Patient Monitoring

Patients may be reassessed periodically, often at:

Several-month intervals during rehabilitation, depending on injury severity.

Monitoring should include:

Range of motion

Quadriceps strength

Posterior drawer laxity

Functional stability

Return to sport or work

Key Principle

The posterior cruciate ligament is the primary restraint to posterior translation of the tibia, and injury classically occurs after a posteriorly directed force to the proximal tibia with the knee flexed, such as a dashboard injury.

Most isolated PCL tears can be managed with:

Nonoperative rehabilitation emphasizing quadriceps strengthening and controlled restoration of motion.

Surgery is primarily reserved for:

Symptomatic high-grade injuries, displaced avulsion fractures, or combined multiligament instability.