Is there a proper name for this part of your body?

There is lots of cartilage back there underneath your patella (knee cap).

Popliteal area... :)

When my hubby starts out rubbing that area, it is the "uwanna"?

From what i found there is no one name ,here is the information I founf hope it helps

From what i found there is no one name ,here is the information I founf hope it helps
The knee is a complex, compound, condyloid variety of a synovial joint which hovers. It actually comprises two separate joints.

The femoro-patellar joint consists of the patella, or "kneecap", a so-called sesamoid bone which sits within the tendon of the anterior thigh muscle (m. quadriceps femoris), and the patellar groove on the front of the femur through which it slides.
The femoro-tibial joint links the femur, or thigh bone, with the tibia, the main bone of the (lower) leg. The joint is bathed in a viscous (synovial) fluid which is contained inside the "synovial" membrane, or joint capsule.
The recess behind the knee is called the popliteal fossa. It can also be called a "knee pit."

The back of the knee is called the popliteal fossa.