A 57-year-old man came to a dentist with complaints of a dull aching pain in the area of his right temporomandibular joint and morning stiffness of the lower jaw. His condition has a wave-like course. throughout the last 3 years. Objectively, the face is symmetrical, the mouth opening reduced to 3 cm. During the movements of the lower jaw, an articular noise and clicking (step-like displacement of the lower jaw) occur in the area of the right TMJ. The skin over the joint is unchanged. Palpation detects no changes in the muscle tone. What is the most likely diagnosis in this case?