膕窩囊腫

Baker's cyst or popliteal cyst (medicine)

knee pit / popliteal fossa (medicine)

popliteal (anatomy) / hollow at the back of the knee

nest / pit or hollow on the human body / lair / den / place / to harbor or shelter / to hold in check / to bend / classifier for litters and broods

to feel vexed / annoyed / good-for-nothing / stupid and cowardly

sack / purse / pocket (for money)

cyst (med.)

to swell / swelling / swollen