Trigger finger occurs when the tendon that controls a finger or thumb can't glide smoothly in the sheath that surrounds it. This can happen if part of the tendon sheath becomes swollen or if a small lump forms on the tendon, which is called a nodule. The condition is most common in women over the age of 50 and in people with certain risk factors such as diabetes, low thyroid function, or rheumatoid arthritis

. It can also be caused by overuse or repetitive movements, and is more common in individuals who perform forceful hand activities