Joints and ligaments · Lower limb
PCL !
The posterior cruciate ligament (PCL) is a strong band inside the knee that stops the shin bone sliding backward.
Official name: Posterior cruciate ligament
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What it is
A thick band in the middle of the knee, just behind the ACL. The two cross like an X.
What it does
Stops the shin bone from sliding backward under the thigh bone.
Key facts
- Attaches
- Posterior intercondylar area of tibia to lateral surface of medial femoral condyle
- Function
- Resists posterior translation of tibia on femur; main stabilizer of the flexed weight-bearing knee
- Tight in
- Knee flexion
Relations
- Course
- From a depression on the back of the tibia, below the joint line, it runs up, forward and medially to the lateral wall of the medial femoral condyle, at the front of the notch
- In front
- ACL, which crosses it in the notch, and the anterior meniscofemoral ligament (of Humphry) when present
- Behind
- Posterior meniscofemoral ligament (of Wrisberg) when present, then the posterior capsule; the popliteal artery lies close behind its tibial attachment
How to find it
Not palpable. At arthroscopy from the front it lies in the notch behind and medial to the ACL, running up to the lateral wall of the medial femoral condyle, often half hidden by the ACL and synovium; its tibial attachment, below the joint line at the back, is viewed through a posteromedial portal.
Examination
- Posterior drawer at 90° of flexion: backward translation of the tibia; grade I keeps some step-off, grade II brings the plateau flush with the condyle, grade III lets it fall behind
- Posterior sag (Godfrey) sign: hips and knees at 90° with the heels supported; gravity lets the tibia sag back and the normal tibial step-off disappears
- Quadriceps active test: from the sagged position at 90°, a quadriceps contraction pulls the tibia forward, which means the PCL is torn
- Dial test (external rotation of the feet, prone): over 10° more than the other side at 30° only points to the posterolateral corner; at both 30° and 90°, to PCL plus posterolateral corner
On imaging
MRI: the normal PCL is a thick, uniformly dark, curved band on sagittal images; a tear shows thickening with high signal, or a gap. Lateral X-ray may show a bony avulsion from the back of the tibia. Stress views (kneeling or with a backward force on the tibia) measure posterior translation against the other knee, useful in chronic tears.
Common problems
- Tear from a hard blow to the front of the shin with the knee bent (such as a dashboard injury) or a fall onto a bent knee.
- Often partial; can occur with other ligament injuries.
How it is diagnosed
Exam tests that check backward movement of the shin bone (posterior drawer, sag sign). MRI and X-rays.
Treatment
- Many PCL injuries are treated with physical therapy and a brace.
- Surgery (PCL reconstruction) for severe tears or when several ligaments are injured.
Clinical notes
- Bony avulsions of the tibial attachment can be fixed directly through a posterior approach and tend to heal well
- Chronic PCL deficiency overloads the medial compartment and the patellofemoral joint, which may wear out over time
- In a knee dislocation both cruciates are usually torn; the popliteal artery is at risk, so pulses and the ankle–brachial index are checked in every case
- Reconstruction grafts: hamstring, quadriceps or bone–patellar tendon–bone autograft, or allograft; the tibial tunnel is drilled close to the popliteal artery
Development
Forms with the ACL from the mesenchyme between the embryonic femur and tibia; the two cruciates are already crossed before the joint cavity has fully opened.
Memory aid
LAMP: the ACL runs from the Anterior tibia to the Lateral femoral condyle; the PCL from the Posterior tibia to the Medial condyle.
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
What are the attachments of the posterior cruciate ligament (PCL)?
Posterior intercondylar area of the tibia to the lateral surface of the medial femoral condyle (LAMP: Posterior to Medial).
What is the classic mechanism of a PCL tear?
A hard blow to the front of the shin with the knee bent, such as a dashboard injury, or a fall onto a bent knee.
Which bedside test is most accurate for a PCL tear, and how is it graded?
Posterior drawer at 90°, graded by tibial step-off: I keeps some step-off, II flush with the condyle, III falls behind it.
What is the posterior sag (Godfrey) sign?
Hips and knees at 90° with heels supported: gravity lets the tibia sag back and the normal tibial step-off disappears, showing a PCL tear.
Which associated injury must always be sought with a PCL tear?
A posterolateral corner injury; missing it is a classic cause of PCL graft failure.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- ligamentum cruciatum posterius TA2 1891
- Official Spanish (DeCS)
- Ligamento cruzado posterior DeCS D016119
- English (TA2)
- Posterior cruciate ligament
- Also called
- ligamentum decussatum posterius
Related
Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Bony Pelvis and Lower Limb: Knee Posterior Cruciate Ligament; Anatomy of the Human Body (20th ed.): Development of the Joints (Lea & Febiger (Gray's Anatomy, 1918), 1918) · adapted, Public domain.
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Representative model, for educational purposes only.
