Tendons and ligaments are dense connective fibers mainly composed of type I collagen. However, the structure, function, and cellular behavior are different between tendons and ligaments. Anatomic, biological, and developmental studies have revealed the distinct differentiation process of tendons, ligaments, and these attachments to the bones (so-called entheses). In addition, arthroscopic devices, surgical materials, and operative techniques for the treatment of tendon/ligament injuries have been dramatically improved. Based on these backgrounds, the treatment strategies of tendon/ligament disorders have changed in recent years. This review focused on the pathology of tendon and ligament injuries involved in the tear of the rotator cuff and anterior cruciate ligament. We also described the current treatment for the tendon/ligament injuries and the future regeneration therapy against these connective tissue injuries.