Thoracic outlet syndrome is a condition in which the nerves or vessels behind the collarbone (clavicle) become compressed or stretched. Arm pain, weakness, or numbness often result.

The arm pain can be similar to angina, which is the pain that is linked with a heart attack. Although angina consists mostly of chest pain, it may start in or spread to the arms.

Symptoms typically occur with lifting the arms to shoulder level or other positions that put pressure on the nerves and vessels behind the collarbone. Treatment includes stretching and strengthening exercises as well as avoiding activities that cause symptoms. In rare cases, surgery is needed to relieve the nerve compression.