Knowledge of rotator cuff tears, especially in young people, and their cause has been vastly expanded in recent years. This is reflected in the understanding of the pathogenesis of these lesions and the specific therapy. In contrast to the mostly degenerative tears in older people, the causes in young, active people differ: traumatic disruption, internal impingement due to instability (PSI, ASI), SLAP lesion, and microtraumatic causes may be found. Recently, connections between the different pathologies like internal impingement and the SLAP lesion were shown. For an accurate diagnosis and differentiation between the different pathologies an exact clinical examination and a high-quality MRI scan with intra-articular contrast enhancer is necessary. The final therapy should be planned based on the causative pathology; then good long-term results will be achieved and return to sports is likely. If there is no structural damage, conservative therapy should be initiated. If there is any structural damage, e.g., SLAP lesion or rotator cuff tear, surgical treatment is indicated. Besides a SLAP repair and rotator cuff suturing, care must be given not to miss an accompanying instability. These instabilities should also be corrected, e.g., with arthroscopic ventral capsular plication, otherwise results are worse.