Ok so my knee is swollen and painful and stiff and this has been going on for two weeks - had an ultrasound and x-ray which were normal what's next?

Varies : It depends on whether or not you had an injury. With an in injury it could many things, from a knee sprain to a cartilage or ligament tear. Without an injury, it could be an infection, gout, or any number of rheumatoid like problems. Either way it sounds like you need a work up for knee pain including an mri.

MRI: If you need to have the best examination, an MRI should be considered by you / your physician if your symptoms/concerns persist.