there are so many causes of lameness and neuro issues in chickens, that every case is really different.  It seems that if they have an injury, it takes a long long time, in most cases, to heal completely.  We just released our limping cockerel, after he'd been confined for three weeks.  He was very lame at first, due to his injury, but was making a slow recovery with the help of baby aspirin three times a day, and B complex 1/4 tab once a day.  And we had him in a cage so he couldn't move around much.  he is still limping, but we decided finally to let him out anyway, and since we have, he's so happy to be free, he seems to be doing better all the time. His limp is only slight though.  We've had other birds with injuries and some still limp, but they have figured out how to deal with it.  Obviously, though, you can't do this if your bird is very lame or has neuro issues. 
 
You need to fully describe the symptoms in every lame bird, so that we can determine what the cause might be, and the best way to maybe fix it.  Neuro issues are not a death sentence either, we helped one of our pullets, who had a serious neuro issue, make a full recovery with the use of Hypericum. 
 
Sometimes, unfortunately, there is no cure.  Vitamin therapy and baby aspirin are good starters.
 
Soaking in warm epsom salts soak helps too.  A couple times a day.