How can a orthopedic diagnose a meniscus tear with a examination? can a displaced meniscus root be repaired? is that considered a tear?

It's possible: There are some findings on physical exam of the knee that would give your orthopaedic surgeon an "impression" that you have a meniscal tear. The best way to confirm this is with an mri. Arthroscopic surgery is usually used to debride (clean up) a torn meniscus and in some cases they can be repaired.

Exam can do it: An examination can lead to a strong suspicion that a tear has occurred but an MRI will be needed to confirm it. It can easily be repaired through an arthroscope.

? dx: Yes you can sometimes tell that a tear has occurred by physical exam but an MRI is very helpful in confirming the dx a root tear is a bit worse than a regular tear they can be repaired but it is technically more complex occasionally some recommend meniscal transplants this is not something that I have any great experience with.

MRI helps too: Pain along joint line with an increase or click with mcmurray (twisting) maneuver. The root can be repaired and yes, it's considered a tear. Mri very helpful in this case.