Flexor tendon and extensor tendon lacerations are usually caused by an injury to the finger, hand or arm. Cuts to these areas can cause simple-looking injuries that may have actually done extensive damage to the intricate groups of tendons, nerves and blood vessels that are critical to proper hand function. Careful evaluation is needed to avoid permanent damage, especially in deep finger cuts. Some athletic activities can cause lacerations, such as wrestling or playing football. Some conditions, such as rheumatoid arthritis, can weaken the tendons, making them prone to tears. Often when the tendon is partially torn, it will eventually completely tear. For complete tendon tears, surgery is almost inevitable as the torn tendon ends pull away from each other at the tear and cannot heal back together on their own.