Thumb injuries usually affect two thumb tendons. These tendons are called the abductor pollicis longus (APL) and the extensor pollicis brevis (EPB).
Thumb Injuries such as Trigger finger or Trigger Thumb can affect tendons that move the fingers. These are held in place on the bones by a series of ligaments called pulleys. These ligaments form an arch on the surface of the bone that creates a sort of tunnel for the tendon to run in along the bone. To keep the tendons moving smoothly under the ligaments, the tendons are wrapped in a slippery coating called tenosynovium.
The condition called de Quervain’s tenosynovitis causes pain on the inside of the wrist and forearm just above the thumb. It is a common problem affecting the wrist and is usually easy to diagnose.
Causes of Thumb Tendonitis
Repeatedly performing hand and thumb motions such as grasping, pinching, squeezing, or wringing may lead to the inflammation of tenosynovitis. This inflammation can lead to swelling, which hampers the smooth gliding action of the tendons within the tunnel. Arthritic diseases that affect the whole body, such as rheumatoid arthritis, can also cause tenosynovitis in the thumb. In other cases, scar tissue from an injury can make it difficult for the tendons to slide easily through the tunnel.
Symptoms of Thumb Tendonitis
Trigger finger and trigger thumb are conditions affecting the movement of the tendons as they bend the fingers or thumb toward the palm of the hand. This movement is called flexion.
Causes of Trigger Finger or Thumb
Triggering is usually the result of a thickening in the tendon that forms a nodule, or knob. The pulley ligament may thicken as well.
The constant irritation from the tendon repeatedly sliding through the pulley causes the tendon to swell in this area and create the nodule. Rheumatoid arthritis, partial tendon lacerations, repeated trauma from pistol- gripped power tools, or long hours grasping a steering wheel can cause triggering. Infection or damage to the synovium causes a rounded swelling (nodule) to form in the tendon. Triggering can also be caused by a congenital defect that forms a nodule in the tendon. The condition is not usually noticeable until infants begin to use their hands.
Symptoms of Trigger Finger or Thumb
At the Centre for Musculoskeletal Medicine we usually diagnose Thumb injuries easily through a physical examination. Most of the time no special tests are required, however distinguishing between different Thumb injuries, which often carry the very similar symptoms can be the major concern.