Thank you for the input! I would also like to add that the "catching" feeling is a classic sign of a "bucket handle" tear where one side is detached. It's hard to explain (I wish I could draw), but try to picture a crater with another layer around the top edge, draw a upside "U" into that layer (hence the bucket handle). Of course if one side of that "U" comes loose, it will leave that section of meniscus the ability to slip into the joint space causing a catch or even a lock. Hope this helps! jd1963
I would also add that for meniscus tear, typically, you will find going down stairs more painful than going up them. That is a question that I would ask an athlete with a possible tear ('Is it harder going up or down stairs?') it is one of classic signs for a meniscus tear.
The catching feeling is meniscus but the instability sounds like it could be ligamentous.
I agree with JD1963 - you should make yourself an appointment with an Orthopod especially with the instability that you are feeling if you haven't already.
Donovan, You should be practicing RICE (Rest, Ice, Compression and Elevation). I would get in to see a Orthopod ASAP. Sorry for the bad news! He/she will probably take some X-rays first (AP/Lat/Oblique and maybe Sunrise views), protocol you know. They will most likely be negative since they won't show soft tissue damage. The MRI on the other hand will seal it. Keep me updated if you have the time. Best wishes! jd1963