Differential Diagnosis for Shoulder Issue Causing Posterior Arm Pain
Single Most Likely Diagnosis
- Subscapularis Tendinopathy or Strain: This condition is a common cause of posterior arm pain due to its location and function. The subscapularis muscle is one of the rotator cuff muscles, and its tendons can become inflamed or strained, leading to pain in the posterior aspect of the arm.
Other Likely Diagnoses
- Rotator Cuff Tendinopathy: Similar to subscapularis tendinopathy, other rotator cuff tendons (supraspinatus, infraspinatus, and teres minor) can also cause posterior arm pain when inflamed or strained.
- Scapulothoracic Bursitis: Inflammation of the bursae between the scapula and the thoracic wall can cause pain in the posterior arm due to the proximity of these structures to the arm.
- Thoracic Outlet Syndrome: Compression of the nerves and/or blood vessels that pass through the thoracic outlet can cause pain in the posterior arm, among other symptoms.
Do Not Miss Diagnoses
- Cervical Radiculopathy: Although less common, cervical radiculopathy (nerve root compression in the neck) can cause pain in the posterior arm. Missing this diagnosis could lead to delayed treatment and potential long-term neurological damage.
- Pancoast Tumor: A rare type of lung cancer that can cause shoulder pain, including posterior arm pain, due to its location at the apex of the lung. Early detection is crucial for treatment.
Rare Diagnoses
- Quadrilateral Space Syndrome: A rare condition caused by compression of the axillary nerve and posterior circumflex humeral artery in the quadrilateral space, leading to pain and weakness in the posterior arm.
- Terminally Staged Conditions (e.g., Metastatic Disease): In rare cases, metastatic disease to the shoulder or arm can cause posterior arm pain. Although uncommon, considering these conditions is important in patients with a history of cancer.