Like the weenis of the elbow, a kneenis is the bit of skin covering your knee

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.

Unbeknownst to many, the knee, like the elbow, has a wenis. This flap of skin is known as the kneenis.

The opposite of wenis; the skin on your knee.

A penis located on the kneecap.

skin on the back of your knee

The stretchy piece of skin on your knee