A 47-year-old patient complains about limited mobility of her lower jaw in the morning; periodical dull pain in the right temporomandibular joint (TMJ) and general joint stiffness. According to the patient, the stiffness disappears throughout the day after joint "exercising". Objectively: the patient's face is symmetric, mouth opening is limited down to 2,5 cm, there is also joint clicking. Median line deviates to the right by 3-4 mm, palpation of the right articular head is painless. What is your provisional diagnosis?