Intersection Syndrome

What is Intersection Syndrome

Intersection syndrome is a condition that causes pain on the thumb side of the back of the forearm, about 2–3 inches above the wrist. In this part of the forearm, muscles that help move the thumb cross over muscles that help move the wrist.

These muscles may swell when they rub together frequently, which interferes with movement of the bands of tissue that attach muscles to bones (tendons). This causes pain when the wrist is moved, because tendons of the wrist and thumb cannot move freely.

This condition usually goes away with proper treatment, including modification of activities that cause pain and swelling.

Intersection syndrome is a tenosynovitis of the extensor carpi radialis longus (ECRL) and extensor carpi radialis brevis (ECRB) tendons, located in the second extensor compartment, which occurs where the two tendons from the first compartment (APL and EPB) cross superficial to those of the second compartment, approximately 4 cm proximal to the wrist.

Similar to the other disorders that result in tenosynovitis, it is seen as high T2-weighted signal intensity within distended fluid-filled sheaths surrounding the tendons of the second extensor compartment.

This is a common overuse cause of distal forearm pain that results from inflammation at the point where the APL/EPB tendons cross over the extensor carpi radialis longus and extensor carpi radialis brevis tendons in the wrist.

This condition is often seen in laborers who perform repetitive dorsiflexion of the wrist or in athletes such as rowers. The area of inflammation is 6 to 8 cm proximal to the radial styloid. There may be swelling and crepitus with active wrist extension.

What are the causes of Intersection Syndrome?

Intersection Syndrome is typically caused by repetitive gripping or squeezing. In some cases, this condition may be caused by a hard, direct hit (blow) or injury to the back of the forearm.

What increases the risk of Intersection Syndrome?

You may have a greater risk of developing intersection syndrome if you do activities that involve a lot of gripping or repetitive motions of the hand or wrist.

These activities include:

• Certain jobs, such as carpentry or landscaping.
• Certain sports, such as racquet sports, rowing, and weight lifting.

What are the symptoms of Intersection Syndrome?

Symptoms of Intersection Syndrome may include:

• Pain and tenderness in the forearm and wrist. Pain may get worse when:
  • Gripping objects.
  • Moving the wrist.
  • Bearing weight through the wrist or hand, such as when you push up out of a chair.
• A feeling or a sound of squeaking or rubbing (crepitation) when moving the thumb or wrist.
• Swelling of the forearm.

How is Intersection Syndrome diagnosed?

Intersection Syndrome may be diagnosed based on:

• Your medical history.
• Your symptoms.
• A physical exam. Your health care provider may ask you to move your wrist and thumb certain ways to check whether you have pain.
• Imaging tests, such as:
  • MRI.
  • Ultrasound. This uses sound waves to make an image of the affected area.

How is Intersection Syndrome treated?

Treatment for Intersection Syndrome may include:

• Resting the affected area and modifying activities that cause your symptoms.
• Icing the injured area.
• A splint to prevent your wrist and thumb from moving for a period of time (immobilization).
• NSAIDs to help reduce pain and swelling.
• An injection of medicine that helps to reduce swelling (steroid). This may be done if other treatments do not reduce your pain.
• Physical therapy.
• Surgery to relieve pressure on your tendons and muscles (decompression surgery). This is rare. Usually, surgery is only done if other treatment methods are not helpful.

Follow these instructions at home:

If you have a splint:

• Do not put pressure on any part of the splint until it is fully hardened. This may take several hours.
• Wear the splint as told by your health care provider. Remove it only as told by your health care provider.
• Loosen the splint if your fingers tingle, become numb, or turn cold and blue.
• Do not let your splint get wet if it is not waterproof.
  • If your splint is not waterproof, cover it with a watertight covering when you take a bath or a shower.
• Keep the splint clean.
• Ask your health care provider when it is safe for you to drive.

Managing pain, stiffness, and swelling

• If directed, apply ice to the injured area:
  • Put ice in a plastic bag.
  • Place a towel between your skin and the bag.
  • Leave the ice on for 20 minutes, 2–3 times a day.
• Move your fingers often to avoid stiffness and to lessen swelling.
• Raise (elevate) the injured area above the level of your heart while you are sitting or lying down.

General instructions

• Take over-the-counter and prescription medicines only as told by your health care provider.
• Return to your normal activities as told by your health care provider. Ask your health care provider what activities are safe for you.
• If physical therapy was prescribed, do exercises as told by your health care provider.
• Keep all follow-up visits as told by your health care provider. This is important.

How is Intersection Syndrome prevented?

• If you start a new activity that involves repetitive wrist movement, start the activity slowly and gradually build up your strength and flexibility.
• Stop any activity that causes pain in your thumb, wrist, or forearm.

Contact a health care provider if:

• Your splint becomes loose or damaged.
• You have pain that does not go away after wearing your splint as long as told by your health care provider.