Irritable Hip (never heard of it before now) which is causing him a lot of distress.
The Dr said he needs complete bed rest for a week and must not put any pressure on it. Tomorrow he's going for a blood test to rule out any possibility of an infection and at some point he needs to go for an MRI to check that there is no serious underlying thing going on.
We just can't believe it and do feel under attack as a family. Anyway, a week at home is going to be interesting to manage - lots of trips to the DVD shop we think! Pray too that neither of us injure backs carrying him around for a week!