A 35-year-old man presents with mild pain in the joints of his fingers and toes for one year. The joints are stiff upon waking up, but the stiffness gradually wears off over a few hours. Hand functions are unaffected. He also experienced an episode of pain in the left knee joint around 3 years ago, which subsided spontaneously, with no aftereffects. His medical and surgical history is unremarkable, and he is not on any medications.