Thoracic Outlet Syndrome: Understanding Arm Pain, Numbness, and Tingling

Reviewed by the Physiotherapy Team at Waterloo Sports Medicine Centre 

Do you experience pain, numbness, tingling, or weakness in your shoulder, arm, or hand? While these symptoms are often associated with the neck or wrist, they can sometimes be caused by thoracic outlet syndrome (TOS). Thoracic outlet syndrome is a condition in which nerves or blood vessels become compressed as they pass from the neck into the arm. Although it can be frustrating, many people improve with conservative treatment, including physiotherapy. 

What Is Thoracic Outlet Syndrome? 

The thoracic outlet is the narrow space between your collarbone (clavicle), first rib, and surrounding muscles where important nerves and blood vessels travel from the neck into the arm. 

Thoracic outlet syndrome (TOS) occurs when these structures become compressed, leading to symptoms in the shoulder, arm, and hand. There are three main types of TOS: 

• Neurogenic TOS: Compression of the brachial plexus (the network of nerves supplying the arm). This is the most common type, accounting for approximately 90–95% of cases.

• Venous TOS: Compression of a vein, which may cause arm swelling, heaviness, or discoloration. 

• Arterial TOS: Compression of an artery, which is uncommon but can affect blood flow to the arm. 

Most people seen in physiotherapy have neurogenic thoracic outlet syndrome.

Common Symptoms 

Symptoms depend on the structures being compressed but commonly include: 

• Pain in the neck, shoulder, or upper back 

• Pain, numbness, tingling, pins-and-needles sensation in the arm or hand 

• Weakness when gripping or lifting 

• Symptoms that worsen with overhead activities 

• Arm fatigue during repetitive tasks 

• A feeling of heaviness in the arm 

People with vascular forms of TOS may also notice swelling, color changes, or a cold sensation in the affected arm. 

What Causes Thoracic Outlet Syndrome? 

Thoracic outlet syndrome usually develops due to a combination of factors that reduce the space available for the nerves or blood vessels. 

Common contributing factors include: 

• Poor posture, including rounded shoulders and forward head posture 

• Repetitive overhead activities 

• Repetitive lifting or carrying 

• Previous neck or shoulder injuries 

• Muscle tightness in the neck or chest 

• Congenital anatomical differences, such as an extra cervical rib 

• Sports involving repetitive overhead movements, such as swimming, baseball, volleyball, or tennis

Who Is at Risk? 

You may have a higher risk of developing thoracic outlet syndrome if you: 

• Perform repetitive overhead work 

• Participate in overhead sports 

• Spend long periods sitting with poor posture 

• Frequently carry heavy bags on one shoulder 

• Have experienced a neck or shoulder injury 

• Have occupations requiring repetitive arm movements 

How Can Physiotherapy Help? 

For most people with neurogenic thoracic outlet syndrome, physiotherapy is considered the first-line treatment. 

Postural Retraining 

Improving posture can help reduce compression around the thoracic outlet by improving the position of the neck, shoulders, and upper back. 

Stretching Exercises 

Gentle stretching may help reduce tightness in muscles that can contribute to compression, including the: 

• Scalenes 

• Pectoralis minor 

• Upper trapezius 

  
  

Strengthening Exercises 

Improving the strength and endurance of the shoulder blade (scapular) muscles, rotator cuff, and deep neck muscles can improve shoulder mechanics and reduce strain on the thoracic outlet. 

Manual Therapy 

Hands-on treatment may help improve mobility of the neck, upper back, ribs, and surrounding soft tissues. 

Activity Modification 

Learning strategies to reduce repetitive overhead strain and improve movement patterns can help prevent symptom flare-ups.

When Should You See a Physiotherapist? 

Consider booking an assessment if you have: 

• Persistent neck, shoulder, or arm pain 

• Numbness or tingling into your arm or hand 

• Symptoms that worsen when reaching overhead 

• Arm weakness or fatigue during daily activities 

• Symptoms that are affecting work, sports, or sleep 

  
  

If you experience sudden arm swelling, significant colour changes, or severe weakness, seek prompt medical attention, as these may indicate a vascular form of thoracic outlet syndrome. 

Experiencing persistent neck, shoulder, or arm pain with numbness or tingling? The physiotherapists at Waterloo Sports Medicine Centre can assess the source of your symptoms  and develop a personalized treatment plan to help you move more comfortably and confidently.