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Understanding Thoracic Outlet Syndrome

What is Thoracic Outlet Syndrome?

Thoracic Outlet Syndrome (TOS) is a condition in which nerves or blood vessels that supply the upper limb become compressed in the neck near the first rib. The symptoms created by these compressed vessels and nerves typically include pain, altered sensation, and muscle weakness in the neck, shoulder, and/or arm. 

TOS is estimated to impact 8% of the population, with a higher prevalence in women than men, and young women being most commonly affected. Although TOS can technically affect the artery, vein, or nerves in the area, it most commonly (95-98% of the time) affects the nerves, specifically a network of nerves called the brachial plexus. The brachial plexus is typically compressed in one of three areas: 

  1. The Interscalene Triangle (between neck muscles);
  2. The Costoclavicular Triangle (between the first rib and collarbone); or
  3. The Subcoracoid Space (under the chest muscle).

© Photo by E-Sports Healthcare

Who is at Risk for Thoracic Outlet Syndrome?

While the exact causes of TOS remain unknown, there are a variety of factors that appear to increase an individual’s likelihood of developing TOS. These factors include: 

  • Congenital features → atypical rib or spine shape decreased space between neck muscles
  • History of neck trauma → whiplash injury, motor vehicle accident or sports-related injury 
  • Postural or work-associated factors → sloped shoulders, work requiring arms to be overhead 

Individuals with TOS often have a combination of these factors. Sometimes, nerves undergoing compression will not present with symptoms until an additional injury or compression occurs elsewhere along the nerve pathway. The entire nervous system is interconnected and therefore tension to the system in any one spot can be exacerbated by tension somewhere else. Additionally, there is some evidence supporting the idea that nerves can become sensitized from one injury, making them more likely to be symptomatic from any subsequent insult, which is sometimes referred to as “double crush syndrome”. 

How is Thoracic Outlet Syndrome Diagnosed?

Thoracic Outlet Syndrome is typically diagnosed through a combination of a subjective assessment, a physical assessment, and possible additional diagnostic tests.

Subjective assessment: 

Your healthcare provider will likely ask you to describe your symptoms and how they have changed over time. They may ask about activities that exacerbate or improve your symptoms and ask you about any previous injuries and other medical conditions.

Physical assessment: 

Your healthcare provider will observe your posture and note any differences in posture between the affected and unaffected side. They will likely ask you to move your upper body (neck, shoulders, elbows, wrists), noting any movements that are restricted or cause pain. They may palpate the muscles of the neck and chest, looking for tender spots, and differences in muscle bulk between the affected and unaffected side. Additionally, they may feel for differences in skin temperature between the two sides. Your healthcare provider may then also ask you to perform specific movements designed to aggravate your symptoms to help ensure that they are correctly diagnosing your condition.

Additional diagnostic tests:

In certain situations, your healthcare provider may order additional tests such as x-ray, MRI, or electrodiagnostic studies.

What is the Role of Physiotherapy in Treating TOS?

Physiotherapy has been shown to help many individuals with TOS. Your physiotherapist will tailor your program to reflect your unique clinical presentation. Depending on the underlying causes of your TOS, your physiotherapist may adopt one or more of the approaches below.


It is often advisable to modify or temporarily avoid activities that exacerbate your symptoms in order to promote healing. Certain body positions are particularly likely to irritate TOS symptoms, and these include positions in which the shoulders are rounded forwards, or the arm is overhead or out to the side. In order to minimize time spent in these positions, postural adjustments and workplace ergonomic modifications may be an important part of avoiding further exacerbation of your symptoms. Additionally, taking frequent movement/stretch breaks is an important part of many TOS rehabilitation programs. 


If your TOS symptoms appear to be caused by tight neck muscles, a stretching home exercise program may be helpful to target those specific tight neck muscles.

Proprioceptive Neuromuscular Facilitation (PNF): 

Muscles that are high in tone can contribute to muscle imbalances or postural deviations that contribute to TOS symptoms. PNF is a technique that can involve contracting a muscle prior to stretching it farther. By doing this, some of the tone is released, allowing the muscle to stretch more.

Improving neck and head positioning: 

TOS symptoms may be exacerbated by poor head posture and deep neck muscle recruitment. In these cases, deep neck flexor strengthening exercises can be useful, which often takes the form of practising tucking the chin without activating the larger, superficial muscles of the neck.

Shoulder blade postural strengthening: 

Some common shoulder postures aggravate TOS symptoms. Exercises to encourage a more optimal position, such as repeatedly repositioning your shoulder blade (called “scapular setting”), can help promote healing. Once you can confidently position your shoulder blade, your exercises can be progressed to challenge you to maintain this new shoulder blade position while performing increasingly difficult movements with or without added weight. The aim of these exercises is to help you develop more productive habitual movement patterns and the muscle strength required to support these movements, in hopes of decreasing the likelihood of aggravating your symptoms as you move about your daily life.

Breathing exercises: 

Diaphragmatic breathing exercises may be helpful for encouraging normal rib and diaphragmatic movement, releasing unnecessary tension in the neck, shoulders, and upper chest, and simultaneously calming the nervous system. Diaphragmatic breathing involves breathing in through the nose and out through the mouth to invite more breath movement in the lower ribs. Some people find it helpful to visualize sending breath down towards the lower ribs or to feel the lower ribs expanding outwards in all directions. Some may also benefit from placing their hands on their lower ribs for tactile feedback. 

Physical activity/cardiovascular exercise: 

Cardiovascular exercise, such as a daily walking program, can improve circulation to healing tissues and improve pain symptoms. Remaining physically active and breaking up sedentary periods of your day with deliberate movement breaks is an important part of maintaining a healthy lifestyle and recovering from a condition like TOS that is linked to sustained postures. 

Calming the nervous system: 

Individuals with TOS may find it helpful to engage in activities that calm the nervous system. These activities vary by individual, but may include a mindfulness or meditation practice, a mindful movement practice (such as Feldenkrais, Tai Chi, Qi Gong, or Yoga), breathing exercises, physical activity, connecting with friends or loved ones, and engaging in other activities that lower your stress and make you feel safe and supported. Check with your healthcare professional before beginning a new movement practice to ensure you won’t aggravate your symptoms


Thoracic Outlet Syndrome is a common condition in which the blood vessels, or more commonly the nerves supplying the upper limb become compressed. Typically, TOS occurs as a result of a combination of congenital, traumatic, and/or postural factors. Physiotherapy can help by improving the postural contributors to your condition and optimizing the environment for healing, allowing you to feel relief from your symptoms and get back to the activities you enjoy! 


  1. Illig, K. A., Thompson, R. W., Freischlag, J. A., Donahue, D. M., Jordan, S. E., & Edgelow, P. I. (2013). Thoracic Outlet Syndrome. Springer London.
  2. Davidovic LB, Kostic DM, Jakovljevic NS, Kuzmanovic IL, Simic TM. (2003). Vascular thoracic outlet syndrome. World J Surg; 27(5):545-550. doi:10.1007/s00268-003-6808-z


Blog Writers: Bella Levi, MScPT Student; Debra Posluns, MScPT Student; Linnea Thacker, MScPT Student

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