A 57-year-old patient came to an orthopaedic stomatology center with complaints about dull pain in the area of his right temporomandibular joint that is getting worse during eating. The disease developed gradually, it began with constrained mandibular motion in the morning that sometimes grew more intensive, sometimes less. Objectively: the face is symmetric, the mouth can be opened up to 3 cm. Opening of mouth is accompanied by articular noise and clicking (step-like dislocation of mandible). Skin above the joint is intact. Muscle tone is palpatory unchanged. What is the most probable diagnosis?