In get a very sharp pain deep in my knee when i cycle. i am a mtb rider and do regular races. pain started in the middle of my outer thigh and moved down into my knee.

Sounds like : iliotibial band syndrome which is a conjoined muscle fascia for the tensor fascia lata and vastus lateralis muscles extending from the anterior iliac crest to the fibular head. You need to give the cycling a break for a few weeks, see a sports medicine physician and follow recommendations. This can be temporarily disabling for an athlete. See photo below. Hope this helps.