Flexor tendon injury
The flexor tendons connect the muscles of the forearm to the bones in the fingers and the thumb. Flexor tendons can be injured as a consequence of a sharp cut to the forearm or hand from a knife, or from glass, or a as a result of the finger catching in machinery (such as a circular saw). Tendons can also be pulled away from their point of attachment as a result of a sudden force applied to the finger or thumb.
There are two flexor tendons to each finger, and one flexor tendon to the thumb. The flexor tendons pass down smooth walled tunnels (the flexor sheath) attached to the undersurface of the fingers and thumb. The flexor sheath holds the tendon in a mechanically efficient position and prevents the tendon lifting away (bow-stringing) from the bones of the hand during flexion of the fingers and thumb.