Tendinitis refers to the inflammation of a sheath surrounding the tendon, known as the tendon sheath, caused by chronic strain. This results in a sterile inflammatory response between the tendon and its sheath, leading to symptoms such as pain and limited mobility. Meanwhile, a tendon sheath cyst is a cystic change occurring within the tendon sheath due to various reasons, characterized by a small amount of fluid or gel-like tissue within the cyst. When tendinitis occurs, it can be managed with conservative treatment, rest, and physical therapy to alleviate symptoms. On the other hand, a tendon sheath cyst might not show evident symptoms initially, but as the condition progresses and the cyst grows, it may compress local blood vessels or nerves causing symptoms, necessitating surgical intervention at this stage.