Shoulder pain is a common problem with a number of different causes. It is the second most common musculoskeletal problem following back pain. It's often a symptom of another problem. There is no reason why you should stop your activities due to shoulder pain. 

There are a number of reasons why you might be experiencing shoulder pain, which include:

• Over exercising, improper use or handling of objects or poor posture.
• Frozen shoulder: a painful condition that reduces the normal movement in the shoulder joint or freezes the joint
• Rotator cuff disorders: dysfunction of the group of muscles and tendons that surround the shoulder joint
• Acromioclavicular joint disorders: the joint at the top of the shoulder with the collar bone
  
• Osteoarthritis in the shoulder joints
• Shoulder instability: where the shoulder is unstable and has an unusually increased mobility
• A broken bone, such as a fracture of the humerus (upper arm bone) or broken collarbone due to fall or trauma
• Referred pain: In some cases, shoulder pain is caused by a problem in another area, such as the neck, that is felt in the shoulder and upper back.