It probably is because the sciatic nerve passes through the gluteal muscles.  However with full-blown sciatica the pain is excruciating and is usually accompanied by weakness in the affected leg.  Walking and even sitting are very difficult and Andy sounded too optimistic for it to be that serious, so hopefully it really is a minor problem which can be sorted out fairly quickly.

UPDATE: Just looked at the Andy at Paris Masters thread where a video has been posted which shows Andy in Paris and already on court practising, so that's encouraging!

Will you post the link please, can't find it?

Thanks for the link! I like the news!

Don't write about this topic, just watch...

Picture with the skirt;

http://www.onthegotennis.com/home/photo-andy-murray-in-a-skirt.html

Full match is on youtube in 11 parts; the 10th:

also on youtube several  practise video's;