Commonly associated with cruciate ligament injuries, injuries to the medial side of the knee
Less common than medial injuries, but more disabling and debilitating
Common cause of failed cruciate reconstruction
Anatomy: Click here
Arcuate fracture:
Avulsion fracture of proximal fibula at PLC attachment, including arcuate ligament and conjoint tendon
Indicator of PLC instability
Strong indicator of PCL tear
Diffuse fibular edema indicates avulsion at conjoint tendon
Edema localized to medial fibular head indicates avulsion at arcuate ligament or PLC
In all PLC injuries, look for fibular head fracture
Segond fracture:
Involves meniscotibial portion of mid-third lateral capsular ligament (MLCL) at superolateral proximal tibia, just posterior to Gerdy's tubercle
Anterior arm of short head of biceps (forms conjoint tendon with MLCL) is also involved
Strong indicator of ACL tear, but may be associated with PCL tear
Anteromedial femoral bone bruise:
Seen in hyperextension-varus injuries with PLC injuries
Anterior rim tibial plateau fracture:
Indicator of PLC injury
Gerdy's tubercle avulsion:
Due to avulsion of iliotibial tract
Difficult to differentiate from Segond fracture on plain radiograph
PLC soft tissue injury grading:
Grade I: minimal
Grade II: partial
Grade III: complete. Best treated within 3 weeks
Lateral collateral ligament injury:
Middle third is most commonly involved
Coronal MR is best with accuracy nearing 100%
Other soft tissue injuries:
Biceps tendon
Arcuate ligament complex - arcuate ligament, fabellofibular ligament, popliteofibulr ligament
Popliteus - at myotendinous junction (associated with cruciate ligament injuries)
Lateral head of gastrocnemius
Take home message:
In all knee injuries look at PLC
In all PLCs, look for cruciate ligament injuries
Reference: Harish S et al. Imaging of the posterolateral corner of the knee. Clin Rad (2006) 61, 457-466
