Sciatica is the name for pain in the buttock or leg caused by irritation of the Sciatic nerve in the lower back.
The sciatic nerve can become very irritable, especially in long term back pain cases. The cause of the back pain may well have settled, most disc and facets do in 6 weeks, but there can often be symptoms that linger. These have several guises, actual pain like aches, but also numbness, pins and needles, burning and weakness.
The mechanical cause of the original back pain irritates the nerve and alters its behaviour. It becomes more irritable and reacts in a very amplified way. The threshold at which the nerve endings send signals to the brain is lower. Thus, the nerve is hyper sensitive to any stimulus, even normal movements.
An assessment with your Physiotherapist will tell you that your symptoms are the irritated nerve and that the mechanical aspect of the problem are resolving. This is helpful from a mental perspective. Knowing what you are dealing with is half the battle.
There is much you and your Physio can do though by working on the nerve mobility and the tightness in the muscles as well as with advice on how best to treat this issue. Actions such as nerve slide and glide work and hands on mobility work to the nerve is hugely helpful.