A 36-year-old female patient complains of intense pain in the knee joints and neck. In the morning she experiences pain in the interscapular region and leg joints; pain subsides after warm-up gymnastics. The patient is overnourished, there is a clicking sound in the knees when squatting, the knees are somewhat disfigured, painful on palpation. Blood test results: ESR - 18 mm/h, WBC- 8,0 × 109/l. Radiography reveals subchondral sclerosis in the left knee. What is the basis of this pathology?