noun
back of the knee; area behind the knee
Anatomical term for the popliteal region; used in everyday contexts as well as medical ones.
膝裏が痛くて、正座ができない。
The back of my knee hurts, so I can't sit in seiza.
膝裏を伸ばすストレッチを毎日やっている。
I do a stretch for the back of the knee every day.
膝 (ひざ) refers to the knee in general, while 膝裏 (ひざうら) specifically means the back of the knee.
Compound of 膝 (ひざ, 'knee') and 裏 (うら, 'back/reverse side').