I think it depends on the type of damage done to your back, and how serious it is. If you pull a muscle in your back, it might take a few weeks to heal. If you sprain your back though (in other words, if you damage a muscle ligament), it can take months to heal properly. If you break a bone in your back, that can be extremely serious and take years to heal; but if you damage your spinal cord in the process, that can potentially be permanent. Were you thinking of a particular type of back trouble?