12 weeks, 6 days

I heard a catchy little tune on the radio and have no idea what it's called or who it's by. Help, please.

It goes something like this:

"I've got bruises on my knees for you... I've got grass stains on my knees for you... I've got holes in my brand new jeans for you..."

Ok, maybe it doesn't say "knees" twice. I think you can understand why I have that word on my mind.

In fact, most of the lyrics may be wrong. I caught the tail end of the song and only heard the chorus once.

What song is this??