HI Xue,
Happy new year to you as well (Except it is not Chinese new year !)
This looks like gout to me,
You can see the synovitis in the joint capsule, and associated hyperaemia,
You can also see crystals deposited on the surface of the hyaline cartilage and this is most likely monosodium urate crystal deposition from gout.
CPPD is possible, but less likely.
If it is CPPD you may see the crystals on a plain x-ray, if it is gout as I suspect you will not see the crystals on the X-ray but you may see some other clues (erosion etc)
Nice one Xue,
Steve