Meniscal flipped fragment
2 days post high speed MVA. Multiple orthopaedic injuries. Left knee haemarthrosis with swelling and pain.
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Massive joint effusion with layering blood products. No loose intra-articular body identified. The fibres of the anterior cruciate ligament are intact although there is oedema within it indicating a low-grade strain injury. The posterior cruciate ligament is intact.
Horizontal cleavage tear the posterior horn medial meniscus, with a small associated flipped fragment in the intercondylar notch. The remainder of the meniscus is intact. The medial collateral ligament is intact, elevated by the joint effusion. Cartilage of the medial compartment is normal. Acute subchondral oedema within the anterior non-weightbearing aspect of the medial femoral condyle, related to the patellar injury.
The lateral meniscus is intact. The lateral collateral ligament is intact although it demonstrates hypointense PD signal in keeping with a low-grade strain injury. Cartilage of the lateral compartment is normal. Focal cortical oedema in the anterior non-weightbearing lateral tibial plateau. Small focus of corresponding subchondral oedema in the lateral aspect of the lateral femoral condyle. The popliteus tendon and posterolateral corner structures are intact, although there is non-specific oedema between the muscles in the lateral calf.
Comminuted patellar fracture, with the dominant fracture line sagittally oriented. Fracture separation measures 15 mm maximally. Fracture haematoma extends posteriorly into the joint space. The quadriceps tendon and patellar ligament are normal. Extensor retinaculum is unremarkable. The iliotibial band is normal. Extensive oedema within in Hoffa's fat pad.
No femoral, tibial or fibular fracture is evident. Popliteal cyst, likely secondary to the joint effusion.
- Comminuted fractured patella.
- Horizontal cleavage tear of the poster horn medial meniscus, with associated flipped fragment in the intercondylar notch.
- Low-grade ACL and LCL strain injury.
Findings confirmed in arthroscopy.
A displaced or detached fragment should be searched for when the entire normal meniscus can't be seen.
The posterior horn is the most common site of medial meniscal injury, likely due to its root attachment.