Possible causes of severe shoulder pain are a dislocated shoulder or a rotator cuff injury, according to Mayo Clinic. With a dislocated shoulder, the upper arm bone, or humerus, pops out of its socket in the scapula, or shoulder blade.
The symptoms of a dislocated shoulder are not only severe pain but a shoulder that is obviously deformed; bruises; numbness and tingling; swelling; and an inability to move the joint, explains Mayo Clinic. The muscles around the shoulder joint may also go into spasm and worsen the pain. A dislocated shoulder can be treated by easing the bones back into place. Sometimes this requires the patient to take a sedative or undergo general anesthesia. However, if the procedure is done properly, the pain of the injury should ease right away.
One type of rotator cuff injury happens when one or more of the tendons that attach the humerus to the shoulder blade is torn, notes the American Academy of Orthopaedic Surgeons. The tear can be partial or full and happen because the tendon is worn down from repetitive stress or because of a sudden injury. These sudden injuries usually cause intense pain. The patient also feels pain when attempting to move his arm or when lying on the injured shoulder.