I am told that people with this condition are hybrids with an alien race called Mefeen.
"mefeen look like the scowling faced what we wrongly call greys. Seems to be a common look away from earth. Their knees are backwards to ours. Anyone with backwards knees is a mefeen hybrid/crossbreed. They are shapeshifters as well but forget about the knees bending and get caught. Hard to know who is a hybrid and who is full blood because of this."