Posterior cruciate ligament (PCL) injury Anatomy

  • This is the strongest ligament in the knee
  • It is regarded as ‘a central stabiliser’. It is the primary restraint to posterior tibial translation
  • Posteromedial bundle (PM): tight in extension
  • Antrolateral (AL): long and thick part, twice the size of PM bundle tightens in flexion
  • Originates from a broad crescent-shaped area in the posterolateral medial femoral condyle
  • It inserts centrally posteriorly 1.0-1.5 cm below the articular surface of the tibia
  • It has an average length of 38 mm and a diameter of 13 mm
  • PCL and quadriceps are dynamic partners in stabilising the knee in the sagittal plane.
  • There are three components

Anterolateral: Long and thick part, twice the size of the posteromedial bundle; tightens in flexion

Posteromedial: Tight in extension

Meniscofemoral ligaments: Mechanically very strong

Anterior: Humphrey’s ligament

Posterior: Wrisberg’s ligament

  • Vascular supply from the middle geniculate artery

Mechanism of injury

  • 3% of all knee injuries
  • Direct injury against the proximal tibia when the knee is flexed 90° is the most common (dashboard injury)
  • Falling on a flexed knee with foot in plantar flexion
  • Forced hyperextension (>30°) is associated with multiligament injury. Most instability is experienced with the knee in 90° of flexion
  • High association with periarticular fractures around the knee. It is recommended that the PCL is examined after fracture fixation as there is 7.8% incidence of PCL injuries27. This is also a 2-5% rate of PCL injury with femoral shaft fractures28
  • Also associated with posterolateral corner (PLC) injury and knee dislocations


  • Injury is often missed in the acute knee
  • Clinical examination is more reliable than MRI scan
  • The PCL may be dysfunctional despite normal MRI
  • MRI scan is a confirmatory study for a PCL injury in acute injury (Figure 17.13 a and b). However, it is only 50% of the time diagnostic in chronic cases; therefore, it should be used with caution
  • Lateral stress view radiographs reveal increased posterior sag on posterior drawer in comparison with the contralateral knee (becoming gold standard)
  • Kneeling stress x-ray shows the degree of posterior translation

Clinical examination

  • Tibial step-off sign/posterior sag sign (medial tibial plateau is anterior to the femoral condyle at 90° flexion in a normal knee)
  • Posterior drawer test at 90°
  • Quadriceps active drawer test. Flex the knee to 60° and control the foot by applying downward force onto bed, then ask the patient to contract the quads. The test is positive when the tibia reduces
  • Posterolateral rotatory instability (dial test prone – Requires two people to perform test accurately):
  • Performed at 30° and 90°. Considered positive if there is a difference >10° of external rotation of the foot. If positive at 30° but not at 90° then it is an isolated PLC injury. If positive at both 30° and 90° then this indicates a PCL and PLC injur

Grading of PCL instability

  • Normal tibial step-off is 10 mm at 90° flexion
  • Instability could be mild, moderate or severe
  • Grade I laxity is when there is a 5-mm step-off
  • Grade II laxity is when there is no step-off (flush)
  • Grade III laxity is when there is -5-mm step-off
  • There is a high association between grade III PCL injury and PLC injury. This highlights the importance of the dial test


In isolation, PCL injury often causes little long-term instability. However, it may lead to medial or PF joint pain at a later date. It is more troublesome in soccer players owing to difficulty in deceleration.

Acute isolated PCL injury is commonly missed as it may present with very little pain in the knee without haemarthrosis. There may be only bruising at the popliteal fossa. Chronic PCL injury on the other hand may present with pain in the medial compartment or anterior knee pain.

Figure 17.13 (a, b) Sagittal and coronal T2 MRI scan revealing a ruptured PCL

It is acceptable to treat an acute, isolated PCL injury conservatively. The knee is kept in extension in a brace with calf support (posterior tibial support, PTS brace) until the pain subsides (4-6 weeks) with quadriceps rehabilitation. Start early passive motion only in the prone position to maintain anterior tibia translation.

Outcome is poor after meniscectomy, or with patellar chondrosis, gross laxity and weak quadriceps. If associated with posterolateral or posteromedial injuries, knee stability is dramatically reduced.

Surgical reconstruction

PCL (open/arthroscopic) reconstruction is recommended:

  • Acute combined ligamentous injuries
  • Acute isolated injury with bony avulsion
  • Symptomatic chronic PCL injuries that failed rehabilitation

Arthroscopic reconstruction, although technically demanding, is safe and commonly performed nowadays. Single bundle and double bundle PCL reconstruction can be performed. Double-bundle reconstruction is technically more demanding. Although both techniques resulted in similar patient satisfaction in a level II RCT as measured by outcome assessment, the double bundle procedure significantly improved knee stability.



PCL (open/arthroscopic) reconstruction is recommended:

  • Vascular injury to popliteal vessels: Posterior to PCL insertion on tibia (close to tunnels) with only the posterior capsule separating it
  • Infection
  • Technical error → imprecise tunnel placement, graft tensioning, insecure fixation


  • Loss of motion
  • Avascular necrosis (medial femoral condyle)
  • Recurrent or persistent laxity (common) when a combined injury is not adequately addressed


  • Good clinical outcome seen in acute primary PCL repair with bony avulsions
  • Mid-substance ligament repair are not advised as they are typically not successful
  • PCL reconstructions are less successful than ACL reconstructions
  • Key is to identify and address all other concomitant ligament injuries. Surgical technique is upon surgeon’s preference. Surgical reconstruction can be performed using an arthroscopic transtibial technique of an open tibial inlay technique. This can be either a single or double-bundle reconstruction

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