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What is Pronator Syndrome

Pronator syndrome is a condition that happens when the median nerve is squeezed (compressed) by a muscle or other structure.

The median nerve is a nerve in your forearm that provides feeling to certain parts of your hand. The condition can cause weakness or tingling in your thumb, index, middle, and ring fingers, or it can cause a dull ache or pain in your forearm.

Several sites of entrapment of the median nerve exist in the forearm.

The median nerve may be entrapped at the lacertus fibrosus, at the lateral edge of the flexor digitorum superficialis, by fibrous bands of the superficial head of the pronator teres muscle, or, most commonly, by the pronator teres muscle itself. Pronator syndrome is the compression of the median nerve by the pronator teres muscle.

The onset of symptoms is usually after repetitive elbow motions, such as chopping wood, sculling, and cleaning fish, although occasionally the onset is more insidious, without apparent antecedent trauma.

Clinically, pronator syndrome manifests as a chronic aching sensation localized to the forearm with pain occasionally radiating into the elbow.

Patients with pronator syndrome may complain of a tired or heavy sensation in the forearm with minimal activity and clumsiness of the affected extremity. The sensory symptoms of pronator syndrome are identical to symptoms of carpal tunnel syndrome. In contrast to carpal tunnel syndrome, nighttime symptoms are unusual with pronator syndrome.

What are the causes?

This condition may be caused by:

Overuse or repetitive motions that increase the size of a muscle in your forearm (pronator teres).
Trauma or a hard, direct hit (blow) to the forearm, resulting in swelling (hematoma).
A birth defect.

What increases the risk?

This condition is more likely to develop in:

People who play sports such as baseball, tennis, or golf.
People who have a job that requires grasping objects and twisting the forearm, such as carpentry.
Adults who are 35–50 years old.
Females.

What are the symptoms?

Symptoms of this condition include:

An ache or pain in the underside of your forearm close to the elbow.
A tingling or prickling feeling (sensation) in your index, middle, and ring finger as well as your thumb.
Weakness in your hand, particularly the pinch grip between your index finger and thumb.

Symptoms get worse with repetitive movement or rotation of the forearm.

The physical findings in pronator syndrome include tenderness over the forearm in the region of the pronator teres muscle. Unilateral hypertrophy of the pronator teres muscle may be identified.

A positive Tinel sign over the median nerve as it passes beneath the pronator teres muscle also may be present. Weakness of the intrinsic muscles of the forearm and hand that are innervated by the median nerve may be identified with careful manual muscle testing.

A positive pronator syndrome test, which is pain on forced pronation of the patient’s fully supinated arm, is highly suggestive of compression of the median nerve by the pronator teres muscle. The middle finger flexor superficialis test may also help confirm the diagnosis. The test is positive if a paresthesia in the median nerve is elicited when with the back of the hand and arm against the examining table, the examiner extends the index, ring, and little fingers while the patient forcefully flexes the middle finger at the proximal interphalangeal joint against examiner resistance

How is this diagnosed?

This condition can be diagnosed based on your symptoms, your medical history, and a physical exam. During your exam, you may be asked to move your hand, fingers, wrist, and arm in certain ways. Doing this will help your health care provider find the source of your pain. You may also have tests, such as:

An electromyogram. This test can show how well the median nerve is working and show if there is too much pressure on it or a nearby nerve.
A nerve conduction study. This test measures how well electrical signals pass through your nerves.
An MRI. This test can show nerve problems.
An X-ray. This test may be done to check for an underlying problem, such as a break or crack in a bone.
An ultrasound. This may be done to check for an injury, such as a tear to a ligament or tendon.

Electromyography helps distinguish cervical radiculopathy, thoracic outlet syndrome, and carpal tunnel syndrome from pronator syndrome. Plain radiographs are indicated in all patients who present with pronator syndrome to rule out occult bony pathological processes.

Based on the patient’s clinical presentation, additional testing, including complete blood cell count, uric acid level, erythrocyte sedimentation rate, and antinuclear antibody testing, may be indicated.

Magnetic resonance imaging (MRI) and ultrasound imaging of the forearm is indicated if a primary elbow pathological condition or space-occupying lesion is suspected. The injection of the median nerve at the elbow may serve as a diagnostic and therapeutic maneuver.

Differential Diagnosis

Median nerve entrapment by the ligament of Struthers manifests clinically as unexplained persistent forearm pain caused by compression of the median nerve by an aberrant ligament that runs from a supracondylar process to the medial epicondyle. Clinically, it is difficult to distinguish from pronator syndrome. The diagnosis is made by electromyography and nerve conduction velocity testing that show compression of the median nerve at the elbow combined with the radiographic finding of a supracondylar process.

Both these entrapment neuropathies can be differentiated from isolated compression of the anterior interosseous nerve that occurs approximately 6 to 8 cm below the elbow.

These syndromes also should be differentiated from cervical radiculopathy involving the C6 or C7 roots, which sometimes may mimic median nerve compression. Cervical radiculopathy and median nerve entrapment may coexist as the “double crush” syndrome.

The double crush syndrome is seen most commonly with median nerve entrapment at the wrist or carpal tunnel syndrome. Thoracic outlet syndrome also may cause forearm pain to be confused with pronator syndrome. The pain of thoracic outlet syndrome radiates into the ulnar rather than the median portion of the hand, however.

How is this treated?

This condition may be treated with:

Rest. You will need to limit activities that cause your symptoms to get worse or flare up.
Steroid or anti-inflammatory medicine. These medicines may be prescribed to help with pain and other symptoms.
A splint or brace. You may need to wear a splint or brace for support until your symptoms improve.
Physical therapy. This involves doing hand and arm exercises.
Surgery. This is usually done only if other treatments fail and symptoms continue for more than 6 months.

Nonsteroidal antiinflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors represent a reasonable first step in the treatment of pronator syndrome. The use of tricyclic antidepressants, such as nortriptyline, at a single bedtime dose of 25 mg, titrating upward as side effects allow, also is useful, especially if sleep disturbance is present.

Avoidance of repetitive trauma thought to be contributing to this entrapment neuropathy also is important.

If these maneuvers fail to produce rapid symptomatic relief, injection of the median nerve at the elbow with a local anesthetic and steroid is a reasonable next step. Ultrasound guidance may help improve the accuracy of needle placement and decrease the incidence of needle-related complications. If symptoms persist, surgical exploration and release of the median nerve are indicated.

Follow these instructions at home:

If you have a splint or brace:

Wear it as told by your health care provider. Remove it only as told by your health care provider.
Loosen the splint or brace if your fingers tingle, become numb, or turn cold and blue.
If your splint or brace is not waterproof:
- Do not let it get wet.
- Cover it with a watertight covering when you take a bath or a shower.
Keep the splint or brace clean.

Activity

Return to your normal activities as told by your health care provider. Ask your health care provider what activities are safe for you.
Do exercises as told by your health care provider.

General instructions

Do not use any tobacco products, such as cigarettes, chewing tobacco, or e-cigarettes. Tobacco can delay healing. If you need help quitting, ask your health care provider.
Take over-the-counter and prescription medicines only as told by your health care provider.
Keep all follow-up visits as told by your health care provider. This is important.

How is this prevented?

Warm up and stretch before being active.
Cool down and stretch after being active.
Give your body time to rest between periods of activity.
Make sure to use equipment that fits you.
Be safe and responsible while being active to avoid falls.
Do at least 150 minutes of moderate-intensity exercise each week, such as brisk walking or water aerobics.
Maintain physical fitness, including:
- Strength.
- Flexibility.
- Cardiovascular fitness.
- Endurance.

Contact a health care provider if:

Your symptoms do not improve in 4–6 weeks.
Your symptoms get worse.

Get help right away if:

Your pain is severe.
You cannot move part of your hand or arm.

Complications and Pitfalls

Median nerve block at the elbow is a safe block, with the major complications being inadvertent intravascular injection and persistent paresthesia secondary to needle trauma to the nerve. This technique can be performed safely in the presence of anticoagulation by using a 25- or 27-gauge needle, although at increased risk for hematoma, if the clinical situation dictates a favorable risk-to-benefit ratio. These complications can be decreased if manual pressure is applied to the area of the block immediately after injection. Application of cold packs for 20-minute periods after the block also decreases the amount of post-procedure pain and bleeding.

Clinical Pearls

Avoidance techniques of the repetitive movements responsible for pronator syndrome are often forgotten in the rush to treatment.

Median nerve block at the elbow is a simple and safe technique in the evaluation and treatment of the aforementioned painful conditions. Careful neurological examination to identify preexisting neurological deficits that may later be attributed to the nerve block should be performed in all patients before beginning median nerve block at the elbow.

Median nerve compression by the ligament of Struthers manifests clinically as unexplained persistent forearm pain caused by compression of the median nerve by an aberrant ligament that runs from a supracondylar process to the medial epicondyle.

The diagnosis is made by electromyography and nerve conduction velocity testing that show compression of the median nerve at the elbow combined with the radiographic finding of a supracondylar process.

The pronator syndrome is characterized by unexplained persistent forearm pain with tenderness to palpation over the pronator teres muscle. A positive Tinel sign also may be present. Median nerve compression by the ligament of Struthers and pronator syndrome must be differentiated from isolated compression of the anterior interosseous nerve that occurs approximately 6 to 8 cm below the elbow.

These syndromes also should be differentiated from cervical radiculopathy involving the C6 or C7 roots that may sometimes mimic median nerve compression.

Cervical radiculopathy and median nerve entrapment may coexist as the double crush syndrome. The double crush syndrome is seen most commonly with median nerve entrapment at the wrist or carpal tunnel syndrome.

Pronator Syndrome Rehabilitation

Ask your health care provider which exercises are safe for you. Do exercises exactly as told by your health care provider and adjust them as directed. It is normal to feel mild stretching, pulling, tightness, or discomfort as you do these exercises, but you should stop right away if you feel sudden pain or your pain gets worse. Do not begin these exercises until told by your health care provider.

Stretching and range of motion exercises

These exercises warm up your muscles and joints and improve the movement and flexibility of your forearm. These exercises also help to relieve pain, numbness, and tingling.