Information about general use of ultrasound, the way it produces diagnostic images and limitations of this imaging modality can be also found here.
Power Doppler imaging
Ultrasound can produce still greyscale images of soft tissues such as muscles, tendons and ligaments and demonstrate patholgy involving these structures.
Ultrasound can reveal normal/abnormal blood flow in the soft tissue structures, helping to differentiate different pathologies. In the above video we can see the abnormal blood flow in an inflamed achilles tendon.
Ultrasound is the only imaging modality which can demonstrate optimally the normal/abnormal movement of soft tissues in real time. In this video we can see the abnormal movement of the distal stump of a completely torn achilles tendon. The distal part of the tendon (right side of screen) moves as the patient's moves his foot. The proximal stump (left side of screen) remains still.