Yesterday there was a guy on a red hardtail, pony tail and a jersey that said Skinny (something) on it. I had come across the guy and dog a few times and was going to say something but didnt want to be "that asshole". Coming to the tabletop of blue decent approaching the jump at high speed the golden dog mix came out where I would have landed from the dizzy trail where I guess his master was riding. I hit the brakes and changed direction to try and miss the dog and basically ended up driving my entire right side of my body into the dirt as I landed badly. Been in the hospital with a traumatic brain injury, blood on the brain and swelling. Just wanted to make you all aware there is some guy riding the trails with an off leash dog.