What is it?

Pronator Syndrome is caused by an entrapped median nerve in the elbow. The median nerve originates from the lateral and medial cords of the brachial plexus of the neck and runs down the arm and through the carpal tunnel in the wrist.

The most common site of entrapment is at the carpal tunnel (which leads to carpal tunnel syndrome), however entrapment can also occur at the elbow. The most common site of elbow entrapment in the forearm is at the superficial and deep heads of the pronator teres muscle.

Symptoms/Risks

Risk factors for entrapment include repetitive, forceful pronation and supination. Activities that can lead to this condition include: rowing, pitching, racquet sports and grip-intensive sports. Nerve damage can also result from trauma at the elbow or muscle hypertrophy.

Symptoms of pronator syndrome may include:

• Pain along the proximal anterior forearm

• Deep, aching pain in the elbow

• Worsens with activity but improvement with rest

• No nighttime symptoms

• Sensory disturbances in the proximal radial palm

• Weakness of the thumb

• May have pain in the forearm over the pronator teres

Sports Medicine Evaluation & Treatment

A sports medicine physician will first evaluate through history and physical exam, which may reveal associated muscle weakness depending on the level of entrapment. Additional findings include decreased sensation in the hand (thenar eminence). There are four tests used to identify pronator syndrome:

1. Patient’s hand held in a handshake and asked to pronate against resistance. Patient will endorse pain with this test indicating pronator teres involvement.

2. With the patient’s palm up, fingers are passively extended and the patient is asked to flex the middle finger against resistance which will contract the flexor digitorum superficialis. Pain with this test indicates entrapment at the flexor digitorum superficialis.

3. Hand gripped as if to arm wrestle with arm pronated and extended against resistance. This will isolate the lacertus fibrosus.

4. Pain with resisted elbow flexion at 120-130 degrees if the median nerve is affected by the ligament of Struthers.

Electromyography (EMG) can be used to detect abnormalities in a small percentage of patients. It is typically used to rule out other injuries, including carpal tunnel syndrome. Imaging is typically done only to rule out other possible conditions.

Treatment typically includes:

• Conservative management over 3-6 month period

• NSAIDs

• Splinting

• Activity modifications

• Flexor muscle stretching and physical therapy

• Consider steroid injection into pronator teres

If conservative treatment does not improve pain after six months, then surgery should be considered.

Injury Prevention

Prevention is based on avoiding repetitive activities. If this is not possible, the patient should ensure equipment is fitted appropriately.

Return to Play

After surgery, mobilization can begin within one week, and it may take up to six months to regain full upper extremity strength.

AMSSM Member Authors
Alyssa Horne, DO and Thomas Stocklin-Enright, DO

References
1) Galgon, Heather; Russel, Jacqueline; Asante, Kwame; Maitin, Ian. Pronator Syndrome. Current Diagnosis & Treatment: Physical Medicine & Rehabilitation 2015. Chapter 17 Polyneuropaties.
2) Rodner, Craig M MD; Tinsley, Brian A MD; O’Malley, Michael P MD. Pronator Syndrome and Anterior Interosseous Nerve Syndrome. Journal of American Academy of Orthopaedic Surgeons May 2013 21(5) 268-275.
3) Wolfe, Valerie M; Rosenwasser, Melvin P; Tang, Peter. Entrapment Neuropathies of the Arm, Elbow, and Forearm. DeLee & Drez’s Orthopaedic Sports Medicine, 67, 771-783.e2