Background <p>Osteochondrosis and osteonecrosis affect epiphyseal and apophyseal ossification centres and lead to structural changes in bone and cartilage. They differ in terms of aetiology, age and prognosis. Osteochondrosis dissecans and Osgood–Schlatter disease primarily affect adolescents, while spontaneous osteonecrosis of the knee (SONK/Ahlbäck’s disease) predominantly occurs in older adults.</p> Objective <p>This article presents four clinical cases to illustrate typical manifestations, imaging diagnostics, and therapeutic strategies for osteochondronecrosis in children, adolescents and adults.</p> Conclusion <p>Magnetic resonance imaging plays a&#xa0;key role in staging and guiding treatment decisions. While lesions in juveniles may resolve spontaneously, unstable or progressive cases often require surgical intervention. Ahlbäck’s disease is associated with a&#xa0;poor prognosis and frequently necessitates joint replacement.</p>