das Gelenk
joint
A movable connection between two or more bones in the body that makes movement possible.
Nach dem Sport tut mir oft das Kniegelenk weh.
After sports, my knee joint often hurts.

joint
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joint
A movable connection between two or more bones in the body that makes movement possible.
Nach dem Sport tut mir oft das Kniegelenk weh.
After sports, my knee joint often hurts.

In a medical context, 'Gelenk' (joint) is often used with verbs such as 'schmerzen' (to hurt), 'sich entzünden' (to become inflamed), 'knacken' (to crack), or 'bewegen' (to move).
Wenn ich lange sitze, schmerzt mein Kniegelenk.
When I sit for a long time, my knee joint hurts.
'Gelenk' (joint) is often the second part of compound words that refer to a specific joint in the body, e.g. 'Kniegelenk' (knee joint), 'Hüftgelenk' (hip joint), 'Schultergelenk' (shoulder joint), or 'Handgelenk' (wrist).
Er hat sich beim Sport das Handgelenk verletzt.
He injured his wrist while playing sports.
The technical meaning can be recognized from words from the field of technology and mechanical engineering, such as 'Roboterarm' (robotic arm), 'Maschine' (machine), 'Konstruktion' (structure), or 'schmieren' (to lubricate).
Das Gelenk an der Tür quietscht und braucht etwas Öl.
The joint on the door squeaks and needs some oil.
connection / association
'Verbindung' and 'Gelenk' can both describe two parts being connected to each other. 'Verbindung' is the general word and can refer to something fixed or technical, for example with cables or components. 'Gelenk' is more specific: it is a movable connection. In the body, a joint connects bones and allows movement; in technology, it connects parts so that they can move. The words can be confused because a 'Gelenk' is a kind of 'Verbindung'. But not every 'Verbindung' is a 'Gelenk'. When movement is important, 'Gelenk' is more precise.

Nach dem Training tut mir das Gelenk im Knie weh.
After training, the joint in my knee hurts.
Der Techniker prüft die Verbindung zwischen dem Akku und dem Motor.
The technician checks the connection between the battery and the motor.