Why does ultrasound hurt i have just had it done on my foot but it was painful the physio had to stop i have got plantar fibromatosis in that spot.?

Therapeutic Ultrsnd: You are getting therapeutic ultrasound which uses a higher energy level and lower frequencies compared to diagnostic ultrasound which is painless. The therapeutic exam cause heating effects and micro-bubbles (cavitation) in the tissues treated which can cause discomfort.

Pressure: In order to get images using ultrasound, you need to have good contact with the area being imaged. This means you have to apply pressure, with the probe, on that area. If you were already tender, the exam could make it worse, for a short time.