Most commonly, a flexor tendon injury results from lacerations (cuts). A laceration to the forearm, hand or wrist can result in injury to the flexor tendons. When a flexor tendon injury happens there can be inability to bend the fingers, thumb or wrist. Even small lacerations can result in significant problems with movement if they occur in an important location. Not all tendon injuries are due to lacerations. In some cases, the flexor tendon injury can occur if the tendon end pulls away from bone, if the tendon ruptures due to wear, or if the tendon-muscle interface separates. In the hand, wrist and forearm lacerations are the most common cause of flexor tendon injury. However, if you lose motion in a part of your arm, then tendon injury, even without a laceration, should be considered a possible cause.