Knee – ACL tear

CASE HISTORY

Effusion instability injury.

TECHNICAL FACTORS

Long- and short-axis fat- and water-weighted images were performed.

KEY IMAGES

This case has no key images.

CASE FINDINGS

• A radial tear is demonstrated anterior horn of the medial meniscus. A vertical longitudinal tear is demonstrated in the outer one-third of the posterior horn. Inner edge fraying is seen in the body. No chondromalacia is demonstrated in the medial compartment. There is an impaction-type fracture in the posterior edge of the medial tibial plateau with approximately 4mm depression. ACL rupture is seen. The PCL is buckled. Anterior tibial translation is associated. 
• There is an oblique-type delicate tear demonstrated in the posterior body-horn junction of the medial meniscus measuring approximately 1cm and involving the outer one-third. Swollen meniscus is demonstrated in the posterior body and posterior body-horn junction. There is bony contusion and microtrabecular injuries seen in the sulcus terminalis with mild depression. The lateral tibial plateau also demonstrates bony contusion without fractures. No chondromalacia is demonstrated in the lateral compartment. 
• The MCL is lax and inflamed more conspicuous in the posterolateral corner structures. Insertional low grade partial tear of the LCL-biceps femoris complex. Popliteofibular ligament grade 1 popliteus muscle strain inferior meniscopopliteal fascicle tear and arcuate sprain. No findings of iliotibial band friction syndrome.
• The patellofemoral cartilage is well preserved. Medial and lateral retinacula are intact as are quadriceps and patellar tendons. Extensive subcutaneous tissue swelling is demonstrated more conspicuous anteromedially. Posteromedial corner tear and virtual rupture involves several fascicles of the semimembranosus tendon including oblique posterior component adjacent to fracture. There is moderate to severe sprain of the pes anserine distally and insertionally. 

CASE CONCLUSION

• Complex pivot shift injury consists of ACL rupture with anterior tibial translation grade 1-2 MCL sprain distal low grade partial tear of the LCL-biceps femoris tendon complex.
• Posterolateral corner tear includes popliteofibular ligament grade 1 popliteus muscle strain inferior meniscopopliteal fascicle tear and arcuate sprain.
• A radial tear in the anterior horn and a vertical tear in the posterior horn red-red zone of the medial meniscus and an oblique peripheral tear at the posterior body-horn junction of the lateral meniscus.
• An impaction type fracture in the posteromedial tibial plateau with 4 mm depression contusions and microtrabecular injuries in the sulcus terminalis and posterolateral tibial plateau moderate posteromedial corner injury and partial tear moderate to severe sprain of the distal insertional pes anserine moderate amount of hemarthrosis. 
• Posteromedial corner tear and virtual rupture involves several fascicles of the semimembranosus tendon including oblique posterior component adjacent to fracture.