1 The most common diagnosis in patients with shoulder pain is bursitis or tendonitis of the rotator cuff.  Rotator cuff tears occur when the tendons of the rotator cuff separate from the bone. Surgery is sometimes necessary for this condition.
https://www.verywell.com/shoulder-pain-2548793
1 The most common diagnosis in patients with shoulder pain is bursitis or tendonitis of the rotator cuff.  Rotator Cuff Tear. Rotator cuff tears occur when the tendons of the rotator cuff separate from the bone. Surgery is sometimes necessary for this condition.
https://www.verywell.com/shoulder-pain-2548793
An injury to the shoulder or surrounding region can cause pain and discomfort. Injury related left shoulder pain is usually quite obvious to a person, particularly if it manifests itself right after the accident that caused the injury. In some cases the pain may not develop immediately after an injury.
http://www.medguidance.com/thread/Left-Shoulder-Pain.html
The most common cause of shoulder pain and neck pain is injury to the soft tissues, including the muscles, tendons, and ligaments within these structures. This can occur from whiplash or other injury to these areas.
http://www.medicinenet.com/shoulder_and_neck_pain_health/article.htm
Rest: The first treatment for many common conditions that cause shoulder pain is to rest the joint, and allow the acute inflammation to subside. It is important, however, to use caution when resting the joint, because prolonged immobilization can cause a frozen shoulder.
https://www.verywell.com/shoulder-pain-2548793
1 Bursitis: A bursa is a sac over the joints to provide a cushion to the joints and muscles. These bursae can become swollen, stiff, and painful after injuries.  Heart attacks: Although the problem is the heart, heart attacks can cause shoulder or neck pain, known as referred pain.
http://www.medicinenet.com/shoulder_and_neck_pain_health/article.htm
1 There are only some ways to ease the pain. These include avoiding stress on the inflected joints, pain medication, swimming, and seeing a physical therapist.  Breast pain - This can cause the left shoulder to become irritated, particularly during hormonal changes during the menstrual cycle, pregnancy or breast feeding.
http://www.medguidance.com/thread/Left-Shoulder-Pain.html
If the accident or injury was quite severe then a broken bone may be the cause of the left shoulder pain. A broken collarbone or shoulder blade will be extremely painful, and will be followed by severe swelling, bruising, and the affected bone may protrude from the body.
http://www.medguidance.com/thread/Left-Shoulder-Pain.html
Left shoulder pain can be extremely concerning, especially when the cause is unknown. The pain may occur when you breathe deeply, making it very difficult to function throughout the day. Left shoulder pain may be the result of normal activities of daily living to serious health conditions.
http://www.medguidance.com/thread/Left-Shoulder-Pain.html
Shoulder pain is an extremely common complaint, and there are many common causes of this problem. It is important to make an accurate diagnosis of the cause of your symptoms so that appropriate treatment can be directed at the cause. If you have shoulder pain, some common causes include: 1  Bursitis | Rotator Cuff Tendonitis. The most common diagnosis in patients with shoulder pain is bursitis or tendonitis of the rotator cuff.  Rotator Cuff Tear. Rotator cuff tears occur when the tendons of the rotator cuff separate from the bone.
https://www.verywell.com/shoulder-pain-2548793
what causes shoulder pain
Shoulder pain is caused by injury to the soft tissues, including the muscles, tendons, and ligaments within these structures. An injury to the soft tissues, including the muscles, tendons, and ligaments within shoulder structure causes shoulder pain.