Finger (DIP) flexion/extension with overpressure (Finger DIP joint flexion/extension AAROM, end range)

Start in a seated position.
Place your affected arm on a table, holding your forearm upright.
Place the fingers of your other hand firmly around the middle bone in the finger to stabilise this area.
Try to bend and straighten the finger at this joint, fixing the hand so as to ensure the movement comes from the correct area.
Use the finger of the other hand to push the movement further.