Rhomboid Strain or Spasm: This is the most common cause of pain over the scapula radiating to the shoulder due to the location and function of the rhomboid muscles, which are prone to strain and spasm from overuse or poor posture.

Scapulothoracic Bursitis: Inflammation of the bursae between the scapula and thoracic wall can cause pain in this area, especially with movement of the scapula.
Subscapular Bursitis: Similar to scapulothoracic bursitis, inflammation of the bursae under the scapula can cause pain that radiates to the shoulder.
Thoracic Outlet Syndrome: Compression of the nerves and/or blood vessels that pass through the thoracic outlet (the space between your collarbone and first rib) can cause pain in the shoulder and scapular area.
Myofascial Pain Syndrome: Trigger points in the muscles of the back and shoulder can refer pain to the scapular area.

Pulmonary Embolism: Although less common, a pulmonary embolism can cause sudden, severe pain that may be referred to the shoulder and scapular area due to irritation of the pleura.
Pneumothorax: A collapsed lung can cause sharp chest pain that radiates to the shoulder and scapula.
Myocardial Infarction: In some cases, a heart attack can cause referred pain to the shoulder and scapular area, especially if the inferior wall of the heart is involved.

Scapular Stress Fracture: A rare cause of scapular pain, usually seen in athletes who participate in sports involving repetitive throwing or overhead activities.
Tumors of the Scapula or Thoracic Spine: Although rare, tumors such as osteoid osteoma, osteosarcoma, or metastatic disease can cause pain in the scapular area.
Referred Pain from Abdominal Pathology: Certain abdominal conditions, like pancreatitis or a splenic rupture, can cause referred pain to the shoulder and scapula due to shared nerve roots.