Hi Nancy,
I'm not sure what variety this is but it is either prunung group 2 or 3. Group 2 plants bloom on old wood in the spring and then again on new wood in the fall. Group 3 plants bloom on new wood during the summer. To get this plant back on track I would prune it as a group 3 plant - This winter after the plant goes dormant or very early next spring I would cut it bact to about 12 to 18 inches above the ground. Remove all of the old growth from the trellis. As soon as the plants sends up new shoots in the spring, fertlize it and water it in. A three to four inch layer of organic mulch around the base of the plant would also be usefull. For more info go to chalkhillclematis.com. They have info on the care of clematis.
George

It certainly does need to be cut back hard next spring. It will really help it and look much better getting rid of all that dead wood.

I agree about hacking it back. It is difficult to tell the exact variety of clematis you have from the picture you provided. It definitely does have bare legs which is quite common what happens to type III clematis when they are never trimmed back.

thank you everyone for the great advice! i can't wait to cut it back next spring because it looks so unhealthy now.

nckvilledudes would a close up picture be more helpful to help ID this one?

There are a lot of purples that are very similar. Might not get a perfect id.

Nancy as BorS says, there are a lot of purple colored clematis out there. A close up might help but then again it might not. Better to try and fail then never try at all!