The lateral meniscus is normally less stable anyway than the medial meniscus, but sometimes it may be really abnormally mobile.
![menisco-tibial avulsion or floating meniscus](/sites/default/files/users/user1/menisco-tibial-avulsion.jpg)
This may be due to damage to that area of the capsule and its connections to the meniscus or damage to the meniscofemoral or meniscotibial ligament on that side
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