Yes, those are knees. They do look like fingertips as presented in the image in the OP, but definitely knees. Look at TruCelt’s link. The punishment my mom had growing up on a farm in Poland was similar: kneeling on dried peas/split peas for a period of time. (I would have that frozen peas would eventually melt and squish.)
I can’t seem to view the picture for some reason, but there have been several of those “skin disease” ads that seemed to be a mashup of human skin (fingers, hands) and the back of a suriname toad that is just starting to give birth.
It’s called “click-bait.” These are not advertisers per se. They are paid to get folks to the page to see the advertisement. So all they want to do is get you curious enough to click ont he picture. Very often you never get an explanation or see the original image again.
The way to find out is to right click and get the URL for the image itself. Then go to google images, and click on the camera icon. Paste in the image URL, and it will search and find all the pages where the image exists. Then you can usually find an explanation.
For some this is a waste of time, for others, it’s an absolute necessity.