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

 

 

Bony Avulsion

 

 

Chronic bony avulsion PCL

 

Posterior subluxation of tibia

 

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

 

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