Double PCL sign

The double PCL sign appears on sagittal MRI images of the knee when a bucket-handle meniscal tear (medial meniscus in 80% of cases) flips towards the center of the joint so that it comes to lie anteroinferior to the posterior cruciate ligament (PCL) mimicking a second smaller PCL.

A double PCL sign from a torn medial meniscus can essentially only be seen in patients who have an intact anterior cruciate ligament (ACL) as this is required to prevent the flipped fragment from migrating further laterally, or not aligning parallel to the PCL ¹.

In a minority of patients, a lateral meniscus bucket handle tear, in the presence of torn ACL, may also give rise to a double PCL sign.

Identifying a double PCL sign is highly specific (98-100%) but of variable sensitivity (27-53%) for the detection of displaced bucket handle tears ¹.

Associated signs include:

• flipped meniscus sign
• fragment-in-notch sign
• absent bow tie sign
• central meniscal fragment

Differential diagnosis

• accessory meniscofemoral ligament (ligament of Humphrey)
  • smaller
  • closely approximated to the PCL
  • normal medial meniscus
• medial oblique meniscomeniscal ligament
  • normal medial meniscus