That's not a grapevine. Not from what I can see. Don't know what plant that is just not a grape.

I'm quite sure it is. Here's another part of the same plant.

Funny, I have a weed growing right next to my concord grapes.. It too looks like a grapevine but the leaves are much thinner and definitely not as dense a vine. Check the base of the vine.

Definitely a grape, and a nice one. I think these are a type of gall- a swollen stem area protecting an insect inside. Carefully slice them open and check for tiny larvae. Not sure which kind though. They don't really harm the vine unless there are lots of them.

That is the grape tumid gall. The insect that causes it is called, not surprisingly, the grape tumid gallmaker. The adult is a type of midge.

The larval stage of the midge actually causes the gall. The galls usually form on leaves, but sometimes on stems, petioles and flower clusters.

It's generally not a major problem although if the gall forms on a flower cluster you won't get any grapes from that cluster. There usually aren't enough around to be an issue.

You can remove the gall if you don't like the way it looks. But since this is essentially an insect that lives on native grapes, it is questionable if removing it or leaving it will have any significant effect on the overall population.