Hyperextension and posteromedial corner injury pattern with Baker cyst rupture, and incidental prepatellar quadriceps continuation
Diagnosis almost certain
Presentation
Hyperextension injury mechanism, knee swelling and pain upon passive rotation.
Patient Data
Age: 35 years
Gender: Male
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- Edema due to bone contusion or undisplaced impaction fracture in the ventral aspect of the medial condyle of the tibia and along the PCL insertion, as well as in the femur adjacent to the trochlear sulcus - pattern in line with sustained hyperextension injury.
- Moderate knee joint effusion and stranding of Hoffa's fat pad.
- The posterior oblique ligament is discontinuous proximally, suggestive of detachment from its femoral insertion. No signs of MCL injury.
- Incidental prepatellar continuation of the quadriceps tendon, with subtle adjacent high signal - possible low grade injury.
- Predominantly infiltrative fluid signal dorsally in the popliteal fossa within which medially an about 25 mm poorly defined cystic lesion can be discerned - findings in line with Baker cyst rupture likely due to aforementioned trauma.
Case Discussion
Hyperextension injury with characteristic bone contusion patterns, as well as rupture of the Baker cyst. Posteromedial bone contusion along with posterior oblique ligament injury indicates significant concomitant valgus stress. Prepatellar continuation of the quadriceps tendon is relatively uncommon, and makes the tendon more susceptible to injury.