It is generally recognised that any medical-surgical activity entails the risk of failure, placing the physician at risk of malpractice claims. In order to protect both the physician and the patient, it is important to identify the risk factors relating to the various pathological situations and assess both the incidence and significance of such risks. Hence, a "Potential Failure Rating" could be devised already during the preliminary stages for every type of medical process. Such a rating would be useful both in clinical and medicolegal settings. This article considers the most common and important risk factors involved in typical diseases of the shoulder, from which a relative failure rating is formulated.