A deltoid tendinopathy is caused by a reduction in the quality of the tendon tissue. This can be caused by over- or underuse and can occur in both younger and older people. A tendinopathy is often accompanied by stiffness and pain in the shoulder. This makes it more difficult to carry out movements. In general, a tendinopathy has a recognizable course, which helps in making a diagnosis. The diagnosis will be made on the basis of the patient's story, physical examination and, if necessary, an additional ultrasound or MRI scan. The physiotherapist will mainly focus on advising and, together with the patient, restoring the balance between load and load capacity.