Presentation
Sport injury and knee pain
Patient Data
Anterior cruciate ligament (ACL): there is a full-thickness tear of the ACL, evidenced by discontinuity and abnormal signal intensity of the ligament fibers on MRI sequences.
Medial meniscus: a bucket-handle tear of the medial meniscus is present. The displaced meniscal fragment is seen within the intercondylar notch, creating the characteristic "double PCL sign" on sagittal images ( the displaced fragment can also be seen in axial images).
Medial collateral ligament (MCL): a grade 1 injury is noted, characterized by mild thickening and increased signal intensity superficial to MCL on T2-weighted images without fiber disruption.
Meniscopopliteal ligaments: tears of both the posterosuperior and posteroinferior meniscopopliteal ligaments are observed.
Lateral head of gastrocnemius muscle: there is a partial tear at its femoral attachment, indicated by focal areas of increased signal and fiber discontinuity.
Arcuate ligament complex: injury to the arcuate ligament located between the popliteal tendon and the lateral collateral ligament (LCL) is identified.
Joint effusion: mild joint effusion is present, suggesting intra-articular inflammation or hemarthrosis.
Case Discussion
This case illustrates a complex knee injury involving multiple structures critical for joint stability and function. The full-thickness tear of the ACL compromises anterior stability of the knee and is a common injury requiring surgical reconstruction, especially in active individuals.
The bucket-handle tear of the medial meniscus is significant due to the displacement of the meniscal fragment into the intercondylar notch, leading to mechanical symptoms like locking and pain. The "double PCL sign" is a classic MRI finding in such cases, where the displaced meniscal fragment mimics the appearance of a second posterior cruciate ligament.
A grade 1 MCL injury indicates mild sprain without complete disruption, often managed conservatively with rest and physical therapy. However, the concurrent tears of the posterosuperior and posteroinferior meniscopopliteal ligaments and injury to the arcuate ligament complex suggest the involvement of the posterolateral corner (PLC). Injuries to the PLC are critical as they can lead to rotational instability and are often overlooked, necessitating careful assessment.
The partial tear of the lateral head of the gastrocnemius at its femoral attachment contributes to posterior knee pain and may affect the dynamic stability of the knee joint.
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