My dog got kicked by a horse, and was knocked out for a minute.When she came to she seemed fine.She is alert and eating and drinking.There was no broken bones or bleeding. Any ideas of what else could be wrong with her? Could she have a concussion?

Serious injuries aren't always apparent to the naked eye. There doesn't have to be bleeding and broken bones or fractures aren't always apparent without more in depth diagnostic like an x-ray.
There could be some trauma, concussion, something broken or fractured, spinal injury that will show later or something like that. They also have a much higher pain tolerance than we do and some much higher than others. Since she got knocked out at least a minor concussion would be a strong possibility.
You should at least call your vet to discuss it with them to be safe. They can go over the dangers, possibilities and what things you need to be watching for or anything you should be doing. They can let you know if they think she should get a quick exam, just in case. Keep an eye on her and watch for anything odd until you speak to them. Hope your baby is okay.