Tendinitis refers to the condition where the tendons and their sheaths, due to excessive flexing and extending activities, develop adhesion and exudation between each other, leading to a painful aseptic inflammatory response. Generally, when tendinitis occurs, there is restricted movement in flexing and extending, as well as localized pain symptoms. Moreover, tenderness is also pronounced in areas where tendinitis symptoms are evident. Therefore, the diagnosis of tendinitis can be made through symptoms and examination, and when necessary, ultrasound and MRI can be used to reflect local swelling and inflammatory responses.