Ultrasound gel for sports injuries?

[W W]

Hi, i just wanted to know if it was imperative that a specific ultrasound gel was used when treating tendinitis on my knee and elbow or whether i could use some other gel with a similar consistency. I have run out of my conductive ultrasound gel and need an alternative whilst i wait for my new order to come through. I understand conductive properties etc will be lost but i want to know whether a) using something else will work but just not be effective or b) using something else will actually be dangerous.

The device i am using is called sonic relief.

Thanks