Ultra-sonic waves are directed into the body via a sound head and are reflected depending on structure and consistency of the examined tissue and bone structures. These echoes are registered by the receptive sound head and are made visible on a monitor. This method is painless and without risk for the patient and is therefore increasingsly used. In many cases radiological examination methods are even replaced by sonographic ones, contrary to the methods with ionising radiation, below certain exposure threshold values, biological damage can be almost ruled out. This method is particularly suitable for assessing injuries, inflammations and signs of attrition in the knee joints.