The 'true' shoulder joint is the glenohumeral joint - where the top of the arm meets the rest of the body. The shoulder complex includes the collar bone at the front, shoulder blade to the back. Therefore shoulder pain can cover quite a large area of different structures.
The shoulder is extremely mobile, more in fact than any other joint in the body. Whilst this makes it extremely useful it's also more prone to injury through overuse and trauma. Because of this rehabilitative exercises, posture and ergonomics form an essential aspect to treatment. Correcting sports or exercise technique may also play an important role in resolving shoulder problems.
Frozen Shoulder (Adhesive Capsulitis) - This occurs when the capsule around the shoulder joint adheres to itself with inflammation. Shoulder movement is greatly restricted and in the acute stage is accompanied by severe pain.
Tendonitis - Inflammation of a tendon. Occurs with most shoulder injuries, pain tends to be increased on movement.
Bursitis - Inflammation of a bursa (fluid filled sac). Often associated with tendonitis, trauma or rotator cuff tear. Characterised by hot swelling with marked pain on movement.
Rotator Cuff - This is a muscle tear. It usually follows trauma and is very painful. A common sports injury.
Impingment Syndrome - Inflammation caused by a reduction of space within the shoulder joint. Often aggravated and indeed caused by frequently using your arms above your head. Associated with Oesteo-arthritic changes to the bones themselves, and frequently accompanied by joint instability.
Instability - Simply when your shoulder is able to move outside its structural limits. If caused by a trauma it is often associated with joint dislocation, and is of-course usually instantly very painful. If non-traumatic onset, it can be caused by repetitive and excessive use particularly through throwing sports or swimming, or indeed you can simply be born with it.
Sharp Pain - Indicates inflammation. This can occur on tendons, bursas or indeed the joint itself.
Ache - Often originates from muscular problems, tightness or overuse.
Restriction - Can occur when the joint itself is involved as with adhesive capsulitis, or more commonly is restricted by pain actually caused by muscle and tendon problems.
Weakness - Again, is often associated with pain, or can be directly caused through nerve involvement.
Numbness n Tingling - Indicates nerve involvement which may originate from the neck and not actually the shoulder.