My dad has a hard knot in the center of his right hand on top of his ring finger tendon. pain comes and goes. could this be dupuytren contracture or ?

See below: Dupuytren's contractures occur on the palmer aspect of the hand and commonly affect the fourth and fifth digit . I would recommend you have your father seeking orthopedic hand surgeon for evaluation of this problem. Good luck thank you.

Lump palm: A common condition is dupuytrens which is not related to typical blunt trauma. Other common problems include scar reaction adjacent to a small cut or blister, an inclusion cyst or foreign body and a ganglion of the tendon sheath where the finger and palm meet. Trigger finger can also give thickened tissue below the skin and subcutaneous tissue while dup is in the subcutaneous tissue.

Yes: Nodules or cords in the palm are often the first sign of dupuytrens. If it is painful or clicks, it may be a trigger finger.