Background

 

Anatomy

 

Size

 

Strength

- 2 x strong as ACL

 

Length

- about the same as ACL

- 38 mm

 

Cross sectional area

- 150% of ACL

- 13 mm diameter

 

2 Bundles

 

 

1.  Anterolateral

- most important

- double the size of the posteromedial

- tight in flexion

- try to reconstruct this bundle

 

2.  Posteromedial

- tight in extension

 

Femoral insertion

 

Half moon

- anterolateral aspect MFC

- much more anterior than the origin of ACL                                                                                                       

- inserts 5mm posterior to articular margin of MFC 

- midpoint is 1 cm posterior to articular margin of MFC                                                                                                                  

- 1 or 11 o'clock

 

Radiographic anatomy of femoral PCL insertion

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3874986/pdf/aob-21-323.pdf

 

Tibial insertion 

 

PCL facet

- 1 cm below joint line

 

Radiographic anatomy of the tibial insertion of PCL insertion

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4519663/pdf/main.pdf

 

Menisco-femoral ligaments

 

Both insert onto femur with PCL

Originate from posterior horn lateral meniscus

At least one present in > half of all knees

 

Humphrey

- <1/3 diameter of PCL

- anterior

 

Wrisberg Ligament

- half the diameter of the PCL

- posterior to the PCL

                                     

Ligament of Wrisberg MRI
                                                                                                                                                                               

Arterial supply

 

Middle genicular artery

 

Nerve Supply

 

Tibial nerve

 

Function

 

Primary restraint to posterior tibial translation

- secondary restraints are posterolateral corner

- posterior translation increased even further if PLC and PCL deficient

 

Secondary restraint to ER and varus
                                                                                                                                                                                                                            

Incidence 

 

10x less common ACL

 

Aetiology

 

Direct trauma

- posteriorly directed force on flexed knee

- dashboard injury

 

Indirect

- forced knee hyper-extension

 

Associated Injuries

 

Multi-ligament knee injury

- posterolateral corner

- posteromedial corner

- ACL

 

Clinical

 

Injury often unremarkable

- knee doesn't feel right

- don't feel pop or tear

- posterior knee pain

 

May complain of difficulties walking down stairs in chronic situation

 

Examination

 

Excessive Recurvatum

 

 

Positive Lachman's

 

Will be positive with both ACL and PCL

 

Posterior sag

- place knee at 90 degrees

- tibia will sag posteriorly

- loss of tibial step off (normal 1cm)

 

 

Posterior drawer

 

Restore step off first (tibia 1 cm anterior to femur) then push tibia back

- Grade 1: < 5mm

- Grade 2: 5 - 10mm

- Grade 3: > 10mm

 

 

Quadriceps Active Test

- patients contracts quadriceps with foot stabilised

- the tibia is reduced anteriorly from its subluxed position by the quadriceps

 

Exclude Associated Ligament injury

 

PLC instability

 

1.  Posterolateral draw with foot ER

 

2.  Dial test

- patient prone, external rotation

- > 10 - 15^o  compared with other side abnormal

- asymmetry 30^o posterolateral corner only

- asymmetry 30 and 90^o, PCL and posterolateral corner

 

 

X-ray

 

Bony Avulsion

 

 

Posterior subluxation of tibia

 

Grade 3 PCL disruption - posterior tibia subluxed behind posterior aspect femoral condyles

 

CT

 

Bony avulsion PCL

 

MRI

 

PCL completely torn

 

PCL midsubstance tear with lengthening

 

PCL tibial avulsion

 

PCL femoral avulsion

 

Arthroscopy

 

May miss tear as is extra-synovial

 

Chronic PCL tear from femur

 

Acute PCL femoral avulsion

 

Apparent ACL laxity due to PCL tear and posterior tibial sag; ACL tension restored with anterior drawer