The ultrasound scans are a sonogram that uses high-frequency sound waves to create an image of part of inside of the body. Most scans last between 15 to 45 minutes and they do not carry the risk of radiation exposure. During the scan the radiographers or the specialist uses a hand held probe which is placed on your skin and moved over the part of your body being examined. A lubricating gel is put on to your skin to allow the probe to move smoothly. In some patients based on the request from the surgeons the radiologist may inject steroid or local anaesthetic into the inflamed area or joint. The advantage of having this injection under ultrasound guidance is that it is more accurate and is targeted to the area where the problem lies.
Ultrasound scans: http://www.nhs.uk/conditions/ultrasound-scan/Pages/Introduction.aspx