For any one else who suffers from sciatica and is not injured to the point of requiring physio

The following method was recommended to me by a message therapist, to relieve pain in the sciatic nerve, while I was on a gruelling 6 day backpacking trip (you can do this in mid hike or run while fully geared up):

Locate the sciatic nerve in your buttock (you will know the exact spot, because when you apply pressure to it with your fingertips, the localized point will be incredibly painful) Find a protruding sharp stick or pointed rock at the appropriate height, and lean against it with all your weight, allowing it to poke you right at the nerve point in your backside. (This really hurts at first, but keep leaning and the pain will gradually subside) and....Voila! a quick fix!

Also before starting out and after your run, do the following stretch (hard to describe but I'll try)

Sit on the floor with your one leg crooked in front of you, with the heel of your foot tucked in towards your crotch and the other leg crooked behind you. Supporting your upper body with your hands and your trunk aligned over your thigh and crooked knee, lean forward and lower your upper body towards the floor and hold the stretch. Repeat with the other leg crooked in front. If you are doing this correctly, you should feel this in the area of the buttock around the sciatic nerve.

Ditto re Jon Hardly's info regarding glucosamine sulphate.