We have what's called the integrated disability evaluation system. I don't know if you were apprised of that during your tour, but essentially that is a way for the service to keep a member in, regardless of branch, if that member wants to stay in. If you lose a limb, or whatever your disability is, they will rate you concurrently with the U.S. Department of Veterans Affairs.
Before, that wasn't the case. You could come out of the military with one rating from the service and one from the VA, which are very different. They've integrated those two now and will give the member the option to stay in if they want it and if their disability does not preclude them from prolonged military service.