I will say that cutting the medial collateral ligament is a pretty simple procedure given that you have a vet who knows what they are doing. However, get the proper diagnosis before-hand.
We'll be asking him. I love my vet, he's just super.
We've got the horse now, and she's just great as a first horse for ecurbh... she's been super safe with him and she's young enough that something simple to fix should be fixed, if that's what it is.