Shoulder related pages:
The shoulder is a ball and socket joint. The ball is the top of the arm bone (humerus) and the socket is part of the shoulder blade (scapula).
Above the joint there is a bony prominence called the acromium. The space between the acromium and the joint is called the sub-acromial space. There is also structure called a bursae in the space. It is designed to provide cushioning between the tendons and the acromium.
To move the joint and control the position of the ball in the socket you have a group of muscles called the rotator cuff. They attach from the shoulder blade to the top of the arm bone, passing through the subacromial space.
The rotator cuff muscles are vulnerable to both tendon damage and degeneration (wear and tear). This gets more likely as we get older. Damage to the tendon can range from inflammation to tears. Sometimes there is a one off incident that causes problems, e.g. a fall or new repetitive activity, particularly if it is an overhead activity. In other cases the damage builds over time to become a problem.
Once the tendon becomes inflamed it swells, filling more of the subacromial pace. This makes it more likely the tendon and bursae will become pinched during movement. This is called an impingement.
If possible, stop the activity that is causing the pain or find a different way to do it. If you are causing pain you are causing further irritation to the muscles and bursae.
Think about your posture. When you are sitting in a slumped position with rounded shoulders, you are reducing the size of the subacromial space, making it more likely to cause an impingement. The aims of physiotherapy are to strengthen the muscles around the shoulder blade, correct posture problems (which can cause the subacromial space to be reduced); stretch any tight muscles and strengthen the rotator cuff muscles.
Adequate pain relief is also essential i.e. medication in order to keep the pain at a manageable level. See you GP or pharmacist for further advice.