A flesh eating inflamation of the patellae, spreading slowly to the tibia and fibula, until gangrene kicks in and urgent amputational surgery is necessary. In most cases it creates a nasty smell and oozes snail-slime-like liquid everywhere, infecting others as it enters the nasal tracts and with even clothing contact.
"Mate, your scansion is vile, get to a clinic NOW!"
"Doctor, I don't know what it is, please help me!"
"I'm sorry sir, it's scansion. I could tell from the putrid smell and torrential oozing from your knees."