There are two main types of finger muscles in humans: flexors and extensors. These muscles are attached to the bone by tendons that are oriented in line with the long axis of the bone. The tendon sheath is a ring-shaped ligament perpendicular to the long axis of the tendon, which is placed on the outside of the tendon to hold it in place. When the finger is bent or straightened, the tendon travels within the tendon sheath and rubs against it. Over time, the tendon sheath ligament becomes edematous, hyperplastic and adhesive, forming chronic inflammation that causes hypertrophy of the tendon sheath and narrowing of the canal. This means that the tendon becomes hypertrophied and has difficulty sliding inside the canal, and sometimes it can get stuck and cannot be straightened or flexed, requiring external force for normal movement. Whenever the finger flexes or extends, the tendon barely slides through the annular narrow tendon sheath ring, resulting in a trigger-like “clacking” sound. The disease is initially characterized by flexion problems, stiffness, and mild pain, but the pain increases with time, especially in the morning. To a large extent, this disease can be described as an overuse disorder, caused by excessive and incorrect movements. Trigger finger is also found in children and is rarely self-healing, so early surgery is recommended.