Knee dislocation

A-Classification:

1-Anterior( Tibia moves anterior in relation to femur ) which is the most common type.

2-Posterior ( second most common type ).

3-Medial.

4-Lateral.

5-Rotatory.

B-Imaging findings:

1-Four components injury including ACL, PCL, one or both collateral ligaments.

2-Bicruciate ligament injury alone is very strong evidence for a prior knee dislocation.

3-

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 C-Associated complications:

1-Vascular injury of the popliteal artery ( in one third of knee dislocation ).

2-Injury of the peroneal nerve ( in one third of cases ).

3-Injury of the popliteus tendon ( which could suggests injury of peroneal nerve ).

ACL Tear.

Partial tear of PCL.

complete tearing of the distal biceps femoris tendon with retraction to the joint line (arrow).

high-grade partial-thickness intrasubstance tearing of the proximal portion of the tibial collateral ligament (red arrow). Marrow edema is present in the medial femoral condyle (blue arrow) and medial tibial plateau, extending into the medial tubercle of the intercondylar eminence (yellow arrow). Extensive edema is present in the surrounding soft tissues.

complete tear of the popliteus tendon near the popliteal sulcus (arrow). The fibular collateral ligament is not visualized, a finding that is consistent with a complete tear of this structure as well.

An adjacent sagittal images reveals complete disruption of the PCL as well (red arrow). A displaced meniscal fragment from a bucket handle tear of the medial meniscus (blue arrow) is also present, creating the so-called "double PCL" sign.

A lateral radiograph demonstrates an non-reduced anterior dislocation of the knee.