I am looking to get into competitive ballroom, but fear the damage those 3 inch heels may due to my knees. Are they required to win comps? ( if so this is very sexist, even though they look great...)

I certainly don't *think* heels are required. However, there are plenty of ballroom shoes with lower heels. I wear a 2.5" heel because I feel more stable on it than a 3".
Some shoe manufacturers offer a heel as low as 1.3".
I feel that wearing some sort of heel will look better on the competition floor. Ultimately, though, you have to be comfortable.

If you don't wear a heel, what will you wear?

Ballet Shoes

I think that ballet shoes would take away from the beauty of the dance......and it might make you appear to dance flat footed......the footwork is really important in ballroom.

Dance ballroom in ballet shoes? I doubt that would go over well. Many pros wear 2.5 inch heels. Did you ever see Ballroom Bootcamp on PBS? It was a show that matched up ordinary people with a pro and had them dance in a Pro-Am comp. One of the amateurs wore 1.5 inch heels in the comp and the judge was all over it. Claiming she looked flat-footed. And that was just a made-for-TV event. I would invest in a good pair of practice shoes with low heels for everyday use.

"Ballet Shoes"

The problem is that ballet shoes don't have any definition to the heel. The heel doesn't necessarily have to be too high (some taller ladies will teach in men's practice shoes), but it does need to be hard and defined.

There are relatively low heel court shoes available. IDSF requires them for child competitors in the younger age group. Adult sizes are not commonly stocked but do exist. They also usually have a fairly wide heel, which moderates the height.

My wife uses ballet shoes to practice in as she has problems with her knees but at a dance or comp she uses high heels.

hm... i'd stay away from the ballet shoes if you're seriously competing.

the heels just look better as far as form goes.

I have to agree