Diseases of tendons have recently increased in importance. This may be due to the increasing popularity of free time sport, but also to the increasing number of treatment possibilities. The origin of damage to the tendons can be explained by a series of mechanisms, of which reduced tissue perfusion and mechanical irritation with microtrauma, which lead to degeneration, can be considered as the most important. Imaging diagnostics plays a significant role in the diagnosis and planning of the therapy of such illnesses. In addition to the conventional x-ray to determine the position of the joint and bony structures, ultrasound can be used to examine the tendons, bursae and tissue.MRI is an excellent method for examining the pathology of tendons due to its exceptional qualities for imaging tissue and joints as well as its high specificity. Using MRI, it is possible to determine the degree of morphological change, make reproducible examinations, as well as determining comorbidity factors or the reasons for the changes early in the illness. It therefore influences surgical decisions and can play a key role in the planning of operations. MRI arthography can-depending on the question-increase the diagnostic power in cases of alterations in the rotator cuff.