Very often, patellar luxation or subluxation after spontaneous setting is difficult to diagnose. Concomitant injuries can be highly misleading during diagnosis. Traumatic luxation almost always results from forces exerted on the knee indirectly and by way of the muscles, and must be differentiated from habitual luxation. When the constitution favors the occurrence of luxation it is not the clinical and radiological results that are relevant to the assessment. Only an exact analysis of the course of events can clarify whether the trauma can be recognized as a basic cause covered by insurance laws.