Pronator Syndrome (Pronator Teres Syndrome). A lesser-known cause of forearm pain, hand numbness, and weakness often mistaken for carpal tunnel syndrome

What Is Pronator Syndrome?

Pronator syndrome occurs when the median nerve becomes compressed in the forearm, most commonly by the pronator teres muscle.

The median nerve starts in the neck, travels through the shoulder and upper arm, passes the elbow, and continues into the hand—supplying sensation and movement to the thumb, index, middle, and part of the ring finger.

As it passes through the forearm, the nerve runs:

• Under the biceps tendon

• Between the two parts of the pronator teres muscle

• Beneath the finger-flexor muscles

• Through the carpal tunnel into the hand

Compression along this pathway leads to pronator syndrome.

Why Does Pronator Syndrome Happen?

The most common cause is increased tension or tightness of the pronator teres muscle, which presses on the median nerve.

Other possible causes include:

• Unusual muscle or tendon attachment pressing the nerve against the forearm bones

• Tight connective tissue (fascia)

• Enlarged biceps tendon bursa

• Overdeveloped finger-flexor muscles

• Anatomical variants present only in some people (e.g. Struthers’ ligament, Gantzer muscle)

Although anatomical variations are congenital, muscle overuse and posture often trigger symptoms.

Common contributing factors:

• Prolonged forearm pronation (desk work, keyboard use)

• Carrying heavy bags on the forearm

• Repetitive gripping or lifting

• Sports overuse

  
  

Symptoms – How It Usually Feels

Symptoms depend on where and how strongly the nerve is compressed, but most patients report:

• Diffuse aching pain in the forearm

• Numbness or altered sensation in the hand

• Burning, tingling, or pins-and-needles

• Symptoms extending from the elbow toward the fingers

• Worsening symptoms during forearm rotation (turning the palm up or down)

Additional signs may include:

• Weakness when bending the thumb, index, and middle fingers

• Difficulty making a fist

• A “blessing hand” appearance when trying to grip

• Poor precision and quick fatigue of the hand

Early symptoms are often mild and easy to ignore, which is why pronator syndrome is frequently diagnosed late.

Diagnosis

During examination, symptoms are typically reproduced by:

• Resisted forearm pronation with the elbow straight

• Stretching the forearm into full supination

• Resisted bending of the middle finger (testing finger flexors)

• Resisted elbow bending with outward rotation (testing biceps involvement)

To assess nerve damage and track recovery, doctors may use:

• Electromyography (EMG)

  
  

Differential Diagnosis – Conditions That Must Be Ruled Out

Pronator syndrome can mimic or overlap with:

• Carpal tunnel syndrome

• Anterior interosseous nerve syndrome

• Neck (cervical spine) nerve problems

• Thoracic outlet syndrome

• Shoulder-level nerve compression

Key difference:

• Pronator syndrome causes both sensory and motor symptoms

• Anterior interosseous nerve syndrome causes motor weakness only

Phalen’s and Tinel’s tests help rule out carpal tunnel syndrome.

Treatment

Conservative (Non-Surgical) Treatment

Treatment starts with patient education and removing the aggravating factor.

Physiotherapy focuses on:

• Releasing tight forearm muscles and fascia

• Improving nerve mobility (nerve gliding)

• Manual therapy of the anterior forearm compartment

• Physical therapy modalities to reduce irritation

Additional support may include:

• Anti-inflammatory medication

• Vitamin B12 supplementation

• Temporary splinting, if needed

  
  

Surgical Treatment

Surgery may be considered if:

• EMG shows significant nerve damage

• Muscle wasting appears

• Symptoms persist despite long-term physiotherapy

Nerve release may be performed using open or endoscopic techniques.

After surgery, physiotherapy remains essential, particularly:

• Scar mobilization

• Fascial release

• Gradual restoration of movement and strength

  
  

When to See a Physiotherapist

Seek professional assessment if you have:

• Forearm pain with hand numbness

• Carpal tunnel–like symptoms that don’t improve

• Weak grip or difficulty with fine hand movements

• Symptoms that worsen with forearm rotation

Early diagnosis can prevent nerve damage and surgery.

References

1. Jaskólski D. J. Clinical Foundations of Compression Syndromes. 2006.

2. Lee H. J. et al. Early Surgical Treatment of Pronator Teres Syndrome. 2014.

3. Presciutti S., Rodner C. M. Pronator Syndrome. Journal of Hand Surgery, 2011.

4. Lee M. J. et al. Nerve Compressions Mimicking Carpal Tunnel Syndrome. JOSPT, 2004.

5. Brotzman S. B., Wilk K. E. Orthopaedic Rehabilitation. Elsevier, 2009.