The case of a patient aged 73 years who, following an accidental fall on a staircase, suffered an acute intraarticular dislocation in the left knee-cap is presented. This exceptional dislocation presented incarceration of the proximal kneecap pole in the femoral intercondylar groove. A reduction was carried out under general anaesthetic due to pain and muscular contraction in the attempts at reduction without anaesthetic. We made a surgical check that ruled out associated lesions to the extensor apparatus, soft parts, joint structures and osteophytes. The patient presented advanced arthrosis, above all femoral-patellar. Following two weeks of immobilisation, the patient restarted mobility. There has been no relapse or other type of complication.