The joint enables the space station's solar panels, which provide electrical power for the space station, to rotate and track the sun.
The grease and debris will be analyzed by engineers back on Earth to see if it can help them figure out what caused a similar joint on the right side of the station to be clogged with metal shavings.
Astronauts will also remove insulation from cameras on the robotic arm of the newest lab they attached last week.
