MRI Knee Normal Vs ACL Tear | Anterior Cruciate Ligament Tears | Sports Injuries Imaging Cases

MRI Knee Normal Vs ACL Tear | Anterior Cruciate Ligament Tears | Sports Injuries Imaging Cases

*Cases

0:00 - Complete ACL Tear
7:16 - Partial ACL Tear
8:45 - Indirect Signs

Normal ACL:
The ACL appears as a hypointense (dark) band
Femoral Insertion: The ACL inserts on the medial aspect of the lateral femoral condyle.
Tibial Insertion: The ACL inserts on the anterior part of the intercondylar eminence of the tibia.
PCL Angle: Angle between line drawn through central part of femoral PCL insertion and line drawn through central part of tibial PCL insertion
Normal PCL angle: Greater 105 degrees
Blumensaat Angle: Angle between the line drawn parallel to posterior surface of femur, along the roof of intercondylar notch (Blumensaat line), and the line drawn along the ACL margin in sagittal view
Normal Blumensaat Angle apex points superiorly
Normal Blumensaat Angle has a negative value
Distance between line drawn tangent to the posterior edge of tibial plateau and line drawn tangent to the posterior edge of lateral femoral condyle = Less than 3.5 mm

Complete ACL Tear Features:
Absence of ACL in its normal location
Abnormal horizontal orientation of ACL

ACL Tear:
Abnormal Blumensaat Angle apex points inferiorly
Abnormal Blumensaat Angle has a positive value

Indirect Signs:
Buckling of Posterior Cruciate Ligament (PCL): Question mark (?) shape of PCL, associated with ACL tear. It is a secondary sign
Bowing of PCL: PCL Angle less than 105 degrees suggests ACL tear
Uncovered lateral meniscus sign: Distance between line drawn tangent to the posterior edge of tibial plateau and line drawn tangent to the posterior edge of lateral femoral condyle = Greater than 3.5 mm (suggests anterior tibial displacement)
Lateral Notch Sign: Abnormally deep depression (Greater than 2mm) in the lateral femoral condyle. It is an indirect sign of ACL tear.
Bone contusion: Focal hyperintense areas in the femoral condyle. Can be associated with ACL tear
Segond Fracture: Avulsion fracture of the lateral tibial plateau. Usually suggests ACL tear. The Segond fracture appears as a small, crescent-shaped fragment of bone avulsed from the lateral aspect of the tibial plateau.