i tore my acl and mcl a few years back and have been having problems with my knees ever since my ski coach said to look at some knee braces for skiing.
I know a guy that has some bad knee problems, not a tore acl/mcl, but it pops out backwards sometimes. He swears by his brace, says it's about the only way he can ski. Don't know the model though... could ask if you want though.
