Knee going 'dead' when running

I have my first half marathon in two weeks ... training has been fine and doing distances of 20km for my long runs.

Just went out for a long run and 9km in my knee went totally dead forcing me to a standstill. 30 seconds later it felt fine so carried on and then 5mins in I started being aware of it feeling bruised/inflamed again so stopped. 

Now an hour later I can't feel any problem with it but obviously I am concerned. I've picked up and knee support and will go see a gp next week (for this and my chest pains mentioned in my other thread ... its been a good week!) but any advice on this would be appreciated. I'm going to give a gentle run with the knee support a go tomorrow, Should I avoid any long runs now until the race day? Was planning to do a 10mile race next week. 

Thank you for advice.

any thoughts? didnt run today as it felt slightly like it had been knocked so stuck to swimming and weights.

I haven't seen your other thread... so I don't know what you've said about 'chest pain'.  But unless you are quite sure it is nothing serious, you shouldn't even contemplate going running.  Or going to the gym.  Who cares about a minor knee injury - or missing a week's training before having an investigation? 

Of course, an undiagnosed chest pain is very likely to turn out to be something very minor... but it's just not worth the risk.  Apologies if you've already explained that the chest pain is definitely not an issue... as I said, I haven't seen the post.

Look after yourself. Wait for the gp to say OK