Frozen shoulder - Causes 

Causes of frozen shoulder 

Frozen shoulder is caused when the sleeve that surrounds the shoulder joint, known as the capsule, becomes swollen and thickened.

The shoulder is a ball and socket joint. The end of your upper arm bone (humerus) sits in the socket of your shoulder blade (scapula).

The shoulder capsule is fully stretched when you raise your arm above your head, and hangs down as a small pouch when your arm is lowered.

In frozen shoulder, bands of scar tissue form inside the shoulder capsule, causing it to thicken, swell and tighten. This means there is less space for your upper arm bone in the joint, which limits movements.

Risk factors

It is not fully understood why frozen shoulder occurs and, in some cases, it is not possible to identify a cause. However, a number of things can increase your risk of developing it. These are outlined below.

Shoulder injury or surgery

Frozen shoulder can sometimes develop after a shoulder or arm injury, such as a fracture, or after having surgery to your shoulder area.

This may partly be a result of keeping your arm and shoulder immobile (still) for long periods of time during your recovery. Your shoulder capsule may tighten up due to a lack of use.

For this reason, it is very important you do not ignore a painful shoulder injury and always seek medical advice.

Diabetes

If you have diabetes, your risk of developing a frozen shoulder is increased. The exact reason for this is unknown.

It is estimated that  people with diabetes are twice as likely to develop a frozen shoulder compared with those who do not have diabetes.

If you have diabetes, your frozen shoulder symptoms are likely to be more severe. You are also more likely to develop the condition in both shoulders.

Other health conditions

Your risk of developing a frozen shoulder may also be increased if you have other health conditions including:

Other shoulder conditions

Frozen shoulder can also sometimes develop in association with other shoulder conditions such as:

  • calcific tendonitis - where small amounts of calcium are deposited in the tendons of the shoulder
  • rotator cuff tear - the rotator cuff is a group of muscles that control shoulder movements

Immobility

Not moving for long periods of time is another risk factor for frozen shoulder. This can sometimes occur if you have to spend time in hospital - for example, after having a stroke or a car accident. 

Page last reviewed: 28/04/2012

Next review due: 28/04/2014

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