Finger lock syndrome refers to a condition that causes the finger to lock in position. It mainly affects the layer of tissue surrounding the tendon on the finger called the tendon sheath. It is a thick tissue that connects muscles to bones. This swelling of the sheath prevents the tendon from sliding smoothly. through the sleeve so that the finger locks into place. People of all genders and ages can get a thumb, but it's more common in people over 45 years of age and more in women than men. High-risk occupations such as dentists, tailors, seamstresses and butchers.