If you are told that you have an overdeveloped or inflated popliteous you may not know if it is a compliment or not. I did not :). Over time I have gone to different massage therapists, even some that volunteered at running events, and nobody has an explanation for the ‘bumps’ behind my knees.
They are symmetrical to each other and can be flexed and relaxed so I believe they are muscles and the closest thing I can find is popliteus.
Despite my love affair with running that I found in my 40’s, I have had these as long as I can remember, although I ran 5 miles at a time with my Pop-Pop on Saturdays when I was 5 and 6 years old.
If anyone else seems to have or have seen this let me know, I am curious.
The popliteus muscle in the leg is used for unlocking the knees when walking, by laterally rotating the femur on the tibia during the closed chain portion of the gait cycle (one with the foot in contact with the ground). In open chain movements (when the involved limb is not in contact with the ground), the popliteus muscle medially rotates the tibia on the femur. It is also used when sitting down and standing up. It is the only muscle in the posterior (back) compartment of the lower leg that acts just on the knee and not on the ankle. The gastrocnemius muscle acts on both joints.
Typically they are not visible from the outside of your body, but apparently mine are grotesque.