There are various possible causes for shoulder pain. One is the soreness of some tendons, which are cord that attaches muscles and bones. Another reason can be soreness of the bursa sac (disorder called bursitis), which is a sac of fluid between tendons, joint and muscles located in the upper part of your shoulder.
Group of muscles and tendons in the shoulder are called rotator cuff. Rotator cuff injuries happen in cases of damage or irritation of shoulder tissues. The main symptoms of rotation cuff injury is pain in the shoulder when you try to raise you arm, which are getting worse at night.
There are several symptoms of rotator cuff disorder, among them; complete or partial tears of tendons of rotator cuff, calcium build up in the tendons, inflammation or soreness of the bursa sac, soreness or inflammation of some tendons, etc.
There are several reasons for injuries of rotator cuff, and some of them may happen in the same time like reduced blood supply to tendons or muscles in the shoulder, overuse of the arm or shoulder due to excessive exercises or activities, arthritic processes in the shoulder joint, degradation of tendons including tearing or thinning, muscle imbalance, joint looseness, repetition of same activities (like vacuuming or rubbing), etc.
Things to do to relieve the pain
The main symptom of rotation cuff injury is pain when you try to raise you arm preventing you to do even simple tasks. In order to relieve your pain, you can try some of those things; in some cases, injection of anti-inflammatory steroids is needed, also taking some anti-inflammatory medication such as naproxen can be helpful. Active rest (you move but do nothing hard), applying of ice on the sore spot and special kind of exercises, which you usually do at the end of the therapy (combination of rotating your shoulder easy in large circles and resistance exercises) can help to relieve pain, too.
Exercises after Recovery
After you recover, you should do some exercises (ask your doctor how), to prevent this injury to happen again. You should focus on rotator cuff exercises in order to strengthen it. You can try to exercise of shoulder joint, by rotating your arm slowly in wide circle motions trough the air. Do these several times a day, and if you feel the pain, stop for a while. Another way to prevent those injuries to repeat is set of aerobic programs. Choose the one that improves the blood flow in shoulder and in regions of tendon and bursa.
In some rare occasions surgery is needed, if some long lasting injury or inflammation wears the shoulder tendon or tear the rotation cuff. If this is the case, you may be feeling a weakness in certain movements of arm, even after the pain is gone and injury is healed.