I had a variety of symptoms when I first tore my ACL. It is completely severed. The main overall feeling was one of instability, but in particular, some things really made it go out.
Stepping down forward onto my toe first would make the knee buckle. Sometimes this would happen going down stairs, but uusually it had to be a greater distance, like off a chair.
Kneeling down is impossible and sitting on my heels makes something snap very painfully, making me want to straighten out the knee immediately.
Pushing off is very weak, and one legged hops are a bit of a joke. Basically it's like having the cliched "trick knee".
I never had it repaired, and after twenty years it's become something I work around. It's actually what got me into fitness, having to strengthen quads and hamstrings to stabilize the knee. ACL replacement and repair are very common and very successful nowadays, so don't despair if that's where you end up.
Good luck.
--Ann
