6 to 8 inches off the ground

It won't kill them, but it's not good practice either.

At any time, cut back broken canes to a bud site below the break, remove dead cane sections and canes that are in the way. Otherwise, don't prune in fall unless you have an all-year growing season. Prune in early spring when growth begins. KO roses actually need very little pruning unless you want to reduce the size.

It's also inappropriate to prune spring-blooming shrubs like azalea and forsythia in the fall. If you wait until after blooming in late spring, they will be much prettier.

You probably didn't kill them, but you didn't do them any favors,either.

Somehow, some folks in Tennessee have decided that roses are the same plants as other shrubs. This leads to some who severe prune as early as late September and again in November. This sort of thing takes strength away from the plants.

Roses don't want to go dormant here. If you cut them in fall, they'll put out new growth in two to four weeks, even though it's not yet winter. That growth will probably be killed in late December, and that earlier cutting will have taken away the stored 'strength' that would go to regrow the plant in spring.

I've watched some Knockout that have been pruned three times this fall. I don't know what the heck the grounds crew thinks they are doing, much less why.

What you should have done (in my opinion) was go through and snip off broken canes. Then in late December go in and prune back for height, depending on how high you want them to be next year.

The winter killed new growth that you are going to get, you'll see it contorted and blackened, you can snip it off in winter as well.

What Michael said! But you probably didn't kill your KOs. they're pretty tough. They may take longer next spring to come back and bloom but they will eventually. Next time tell your neighbor that roses should never be pruned in the late fall in cold regions. They store their energy to come back with in the spring in those canes. And I never prune down that low unless I have to because of winter die back. Usually down to 12 to 18 inches is sufficient.

There is always a positive side. Severe prunning is one of the "new" recommendations if one is threatened by Rose Rosette Virus. It removes the overwintering "homes" of the mites.

give them extra food and TLC next spring. Don't be angry with yourself for this

People do that all the time here without to many problems besides them growing back slowly the following season.

But it is a bad practice for sure and one I do not personally follow...
So I agree with what Michaelg and others have said.

My parents have the mow and blow guys whack the ever loving heck outta our Knockouts each year. They always rebound with a vengeance. Knockouts are extremely hard to kill. I wouldn't repeat the procedure, but I seriously doubt they'll kick the bucket.

Josh