Joints ultrasound is a method often unfairly underestimated and replaced by X-ray. But it provides as much if not more information, than an X-ray can.
First its advantage over X-ray is, of course, absence of harmful irradiation. Ultrasound is completely harmful and can be performed as many times a year as needed. The image is created not by harmful X-ray irradiation, but by the properties of the tissues to reflect sound.
Second is that we can receive an image of the joint in much more projections, that standard X-ray can provide. Moreover, we can receive an image in real time, without waiting for the result. We can even see the joint while you move it and thus see a reason for pain or discomfort while moving.
And third, we can combine the diagnostic with the treatment. After confirming the diagnosis, the prescribed medicine can be delivered directly to the joint cavity under ultrasound control.