Knee | Cruciate ligaments | Posterior Cruciate ligament tear: MRI / X-rays

27 years-old woman, with previous hyperextension knee injury during gymnastics.

Clinical examination find a posterior instability on the left knee.

 

Figure 1: AP-view (A) and lateral-view (B): a spontaneous posterior sag is observed on the lateral view.

 

Figure 2: Skyline view: « Tibial drop off » sign on the left knee: increased distance from the trochlear throat to the tibial anterior tuberosity.

 

Figure 3: MRI 3D proton density ponderate with fat-sat sequence. Contusion of the external tibial plateau and the external condyle, predominant in the anterior regions (A, white arrows). Anterior cruciate ligament integrity (B, blue arrow).

 

Figure 4. MRI 3D proton density ponderate with fat-sat sequence. Sagittal view (A): proximal PCL tear (red arrow). Horizontalisation of the distal stump (yellow arrow). Frontal view (B): Marked intra-ligamentous hypersignal on the PCL (green arrow).

 

 

The posterior cruciate ligament (PCL) provides a role in anteroposterior stabilization of the knee, and limitation of hindlimb tibia.
Its involvement is less common
than anterior cruciate ligament tears, between 3 and 20% of ligamentous lesions of the knee.
3 main mechanisms of LCP lesions are:
- Direct anteroposterior trauma in hyperflexion (dashboard syndrome).
- Passive forced hyperextension (sports trauma).
- Varus / valgus and rotational high-energy trauma, realizing an internal or external pentad.

 

X-rays:
- Posterior drawer possible, sensitized by
stress radiographs
-
Possible bony avulsion of the retrospinalsurface

MRI:
- Recent tear appears as a focal area of high T2-signal with irregular margins of the fragment and flattening of the distal part
.
- Recent partial tear: focal signal abnormalities with persitent normal fibers
- Former tear:
thinning and sinuous contours of the ligament.
- Associated lesions: frequent tear
of the medial meniscus (30 to 50%). Anterior tibial and condylar bone contusions. Collateral ligament tears (25 to 50%) with predominant involvement on the medial collateral ligament. Associated ACL tear in 30 to 65% of cases.

 

References:

- PUDU G., GIANNI E., CHAMBAT P., DE PAULIS F. The axial view in evaluating tibial translation in cases of insufficiency of the posteriorcruciate ligament. Arthroscopy 2000; 16: 217-20.

- ANDERSON M.A., SIMEONE F.J., PALMER W.E., CHANG C.Y. Acute posterior cruciate ligament injuries: effect of location, severity, and associated injuries on surgical management. Skeletal Radiol. 2018 Nov;47(11):1523-1532.

- RICHARDI G., LOUSTEAU O., VIALA J., BARBUT J.P., SANS N., RAILHAC J.J. Rupture du ligament croisé postérieur: Apport de l’IRM. Le genou: une approche pluridisciplinaire. GETROA éd., Montpellier, Sauramps Médical; 2006.