Soft tissue injuries. Common symptoms of soft tissue injuries are headaches, muscle spasms, and stiffness. The soft tissue of the shoulder is usually the most vulnerable to injuries. 

Rotator cuff tear. Tears can be caused by a single injury or repeated stress. Pain at night or while resting on the affected shoulder, pain while moving your arm in certain ways, or weakness when lifting your arm can be a telling sign.  

Muscle tears. Tears can be big or small and in most cases a small tear will lead to a bigger tear if not properly treated. There are many causes of tears including playing sports, doing chores, lifting heavy objects, etc. 

Poor posture and sleeping positions. Simple changes in your posture can improve your shoulder pain. Try rolling your shoulders up and back, then letting them relax down, tucking your chin down lightly, and sitting up from your hips. 

Joint overexertion. Occurs when joints in the shoulder go through repetitive motions causing them to over-rotate. Sports like swimming or baseball can contribute to this injury.  

Inflammation of shoulder tendons. Usually occurs due to sports injuries or improper sports technique which causes overload on tissues. This condition usually occurs overtime and symptoms can vary from pain, swelling, clicking noises when raising your arms, stiffness, or a loss of mobility.