Adhesive Capsulitis (Frozen Shoulder): This condition is common in women, especially after the age of 50, and can cause intense pain and stiffness in the shoulder joint without any known injury. The pain can also radiate under the clavicle.

Rotator Cuff Tendinitis: Inflammation of the tendons surrounding the shoulder joint can cause pain in the shoulder and under the clavicle, especially with movement.
Bursitis: Inflammation of the fluid-filled sacs (bursae) that cushion the joints can cause pain and swelling in the shoulder area.
Referred Pain from the Cervical Spine: Cervical spine conditions such as herniated discs or osteoarthritis can refer pain to the shoulder and under the clavicle.

Myocardial Infarction (Heart Attack): Although less common in women, myocardial infarction can present with atypical symptoms, including pain in the shoulder and under the clavicle, especially if the pain is accompanied by other symptoms such as shortness of breath or chest discomfort.
Pulmonary Embolism: A blood clot in the lungs can cause sudden onset of shoulder pain, especially if the clot is located in the upper lobes of the lungs.
Thoracic Aortic Dissection: A tear in the aorta can cause severe pain in the chest and shoulder area, which can radiate under the clavicle.

Pancoast Tumor: A rare type of lung cancer that can cause shoulder pain and weakness due to compression of the brachial plexus.
Osteonecrosis of the Humeral Head: A rare condition where the bone tissue in the shoulder joint dies due to lack of blood supply, causing severe pain and limited mobility.
Polymyalgia Rheumatica: An inflammatory condition that can cause widespread muscle pain, including in the shoulder and under the clavicle, especially in older adults.