Not whole legs, just joints (5)
I believe the answer is:
knees
'joints' is the definition.
(I know this)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for knees that I've seen before include "Lap" , "Leg joints" , "Hinged joints" , "Hinge joints" , "Legs' joints" .)