Between Thanksgiving and Christmas, citizens in the United States eat too much, and watch a lot of football. They also get out in the backyard, and play the game, typically "touch" or "flag football".
In this case, a 38 year-old male was playing flag football, and sustained an injury. His knee swelled almost immediately, and he had an MRI a few days after the injury.
There is an obvious ACL tear:
A coronal image through the posterior knee identifies the medial meniscus (green arrow), but the posterior horn of the lateral meniscus is missing in action, with only fluid found in the expected location of the lateral meniscus (red arrow):
A coronal image through the mid-joint reveals that the torn posterior horn has been flipped out of the joint:
An axial image identifies the torn, flipped meniscus (red arrow), situated between the fibular collateral ligament (yellow arrow) and the popliteus tendon (green arrow).
Most flap tears of the meniscus that are displaced out of the joint are found inferior to the joint line, but these flap tears can also displace superiorly, as in this case. MRI can provide valuable preoperative information, allowing the surgeon to counsel the patient and plan his surgical approach.
Football is a great sport (both the American and European versions), but it does come with its risks...
Vic David MD