Hummmm. True LLD'S are very common but very often give no symptoms at all. If your LLD has been measured by a tape measure and 2 different boney bits (hip and ankle) there is a huge amount of skin slide and measuring discrepancy.
A 4mm short LLD may be only 2mm but the skin slide and poor measurement gives 4mm. You are now given a raise of 4mm to correct, but only 2mm is needed. You now made your short leg, long by 2mm and your long leg short by 2mm....
Trying to change a LLD is like dealing with the devil. You don't need to and will always be the source of a constant irritation. I'm with M....eldy on this....