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Anatomy · Joints & cartilage

Posterior cruciate ligament

The stronger of the two cruciates

Lower limb · inside the knee

The posterior cruciate ligament (PCL) is the thicker and stronger of the two cruciate ligaments in the knee. It runs from the posterior intercondylar area of the tibia upwards, forwards and inwards to the lateral face of the medial femoral condyle. It stops the tibia from sliding backwards on the femur, supports the flexed knee and is most often injured by a blow to the front of the shin.

How to spot them

  • ▸Attaches to the posterior intercondylar area of the tibia, extending slightly down its back surface
  • ▸Runs upwards, forwards and medially to the lateral surface of the medial femoral condyle
  • ▸Crosses the front cruciate inside the notch between the condyles (hence 'cruciate')
  • ▸Taut when the knee is bent; tested by the posterior drawer test and 'sag' sign

What to know

The stronger and thicker of the two crossed ligaments inside the knee: it stops the shin bone sliding backwards on the thigh bone

Posterior cruciate ligament — resists posterior translation of the tibia.

Often torn by a blow to the front of the upper shin with the knee bent, as when a car occupant's knee hits the dashboard

Posterior cruciate ligament — the 'dashboard injury'.

It supports the bent knee, especially when walking downhill or down stairs

Posterior cruciate ligament — the main stabiliser of the flexed knee.

Its femoral attachment is on the medial condyle, while its partner's is on the lateral

Posterior cruciate ligament — it crosses the anterior cruciate.

With the knee bent to a right angle, the tibia appears to sag backwards: a clinical sign of its failure

Posterior cruciate ligament — the posterior sag sign.

Key ideas

  • The cruciates cross like the letter X seen from the side, and are named by their tibial attachments: the ACL in front, the PCL behind.

Quick-fire facts

  • •It is roughly twice as strong as the ACL and is injured much less often.
  • •It supports the knee when flexed (OpenStax).
  • •The posterior drawer test is the classic clinical test of PCL integrity.
  • •Injury mechanisms: dashboard injury, or a fall on the flexed knee with the foot plantarflexed.
  • •It is intracapsular and extrasynovial, like the ACL.
  • •Isolated PCL injuries are often managed without surgery.
  • •Its two bundles are the anterolateral and posteromedial, the former taut in flexion.

Drill it — 7 cards

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Sources