Frozen Shoulder (Adhesive Capsulitis) Causes, Stages, Symptoms, Treatment

The shoulder is a ball and socket joint formed by the upper arm bone (humerus) and shoulder bone (scapula). It is this joint that allows the entire arm to move in various directions. This range of motion can be affected in various conditions, like with a fracture of bones in the shoulder joint, muscle spasm and injuries to the shoulder area. However, there is one condition that can cause pain and stiffness of the shoulder joint for no clearly identifiable reason.

What is adhesive capsulitis?

Adhesive capsulitis is the medical term for frozen shoulder syndrome (FSS), which is usually referred to just a frozen shoulder. It is a condition of unknown cause where the shoulder joint is painful and the movement is limited. The stiffness is the reason why adhesive capsulitis is known as a frozen shoulder. It develops gradually and worses over time. Frozen shoulder can last for anywhere from one to three years with most cases resolving within two years.

Joints are formed when two bones meet and form a structure that allows for one bone to move to some degree. The shoulder joint allows for movement of the entire upper limb. The joint is lined by the synovial membrane which secretes fluid into the joint. The synovial fluid provides lubrication. The entire joint is surrounded by a capsule which contains the synovial fluid. It is this capsule that becomes inflamed in frozen shoulder.

  • Frozen shoulder syndrome affects about 2% to 5% of the general population in the United States.
  • Women are more commonly affects and it tends to occur more frequently in the 40 to 60 year age group.
  • Both shoulders may be affected with frozen shoulder syndrome but it is rare for it to occur at the same time. It is more likely for one shoulder to be affected after the other.
  • Diabetics tend to be about 5 times more likely to be affected with frozen shoulder than non-diabetics.

Read more on facts about frozen shoulder.

Causes of Frozen Shoulder

The exact cause of a frozen shoulder is unknown. Studies have indicated certain risk factors. For example, frozen shoulder is more likely to occur in people who had immobilized the shoulder for long periods or among diabetics. However, the exact causation is still not understood conclusively. It is also believed that frozen shoulder may be due to an autoimmune mechanism, at least in part.

The following process occur in frozen shoulder syndrome for unknown reasons:

  • The joint capule becomes inflamed and this is possibly immune-mediated.
  • Fibrosis with adhesion formation occurs in the synovial lining.
  • The capsule beomes thickened and contracts.
  • The volume within the joint spaces reduces.

In primary frozen shoulder syndrome, there is no preceding event and initial shoulder pain and stiffness may be incorrectly attributed to other shoulder conditions. In secondary frozen shoulder syndrome, there is an event that precedes the start of the symptoms. This includes events like injury to the arm or surgery of the upper limb.

Who is at risk of frozen shoulder?

Women, particularly those older than 40 years of age, are at a greater risk of developing frozen shoulder. Any condition that reduces movement at the shoulder joint is another risk factor. This includes a range of upper limb and shoulder conditions which leads to immobilization. Apart from diabetes, there is also a greater risk of frozen shoulder with conditions such as hyper- or hypothyroidism, Parkinson’s disease, ischemic heart disease, cervical spine conditions and tuberculosis (TB).

Is frozen shoulder the same as arthritis?

Arthritis is a term for inflammation of the joint. Two types of arthritis are common – osteoarthritis (OA) and rheumatoid arthritis (RA). Osteoarthritis is a result of wear and tear of the joint cartilage while rheumatoid arthritis occurs when the immune system attacks the joint lining. Although frozen shoulder involves inflammation of the capsule, it is not considered as a type of arthritis.

Stages and Duration of Frozen Shoulder

As mentioned, the symptoms of frozen shoulder develop gradually and may last for variable periods of time. The duration of each stage can be helpful in identifying the progression of the condition as well as the remaining time before the condition resolves.

  • Freezing stage: Up to 9 months
  • Frozen stage: 4 months to 20 months
  • Thawing stage: 5 months to 26 months

It is often difficult to isolate the exact time when these symptoms start or when one phase moves into the next.

Signs and Symptoms

Pain and stiffness of the shoulder are the hallmark symptoms of frozen shoulder. This is best described according to the different stages/phases. With regards to stiffness, it is usually described as restriction of both active and passive motion of the shoulder. It is important to understand what these terms mean.

Active motion refers to unassisted movement by the action of the a person’s muscles. Passive motion refers to movement without use of the person’s muscles, usually when the movement is done by another person such as when a medical professional moves the arm at the shoulder joint.

Freezing Stage

Shoulder pain with movement becomes progressively worse. The pain is usually described as a dull pain or aching. This pain tends to be diffuse and worse at night which can affect sleep. Movement also becomes limited  The freezing stage is also known as the painful stage.

Frozen Stage

The stiffness of the shoulder joint worsens progressively and range of motion of the shoulder is severely impared. Therefore this is also known as the stiffening stage. Pain usually does not worsen further in this stage. Instead the pain may diminish or stay the same.

Thawing Stage

Gradually the range of motion of the shoulder joint begins to improve. This means that stifness eases slowly. Although the duration of this phase may vary significantly, most people find a significant restoration of the range of motion within 9 months once in the thawing phase.

Treatment of Frozen Shoulder

There is no cure for frozen shoulder syndrome. The goal of treatment is to manage and possibly relieve the pain and stiffness. Exercise, physical therapy and medication are the main therapeutic approaches and sufficient for most cases of frozen shoulder syndrome. Only if these measures are not providing any sufficient benefit then surgery is considered. However, it should be delayed or avoided as far as possible.

Read more on frozen shoulder exercises.

Some of the medical treatments for frozen shoulder may include:

  • NSAIDs (non-steroidal anti-inflammatory drugs) such as ibuprofen.
  • Corticosteroids, oral or injected into the joint.
  • Manipulation of the joint to loosen the stiff tissue of the shoulder tissue.
  • Distension of the joint by injecting sterile water into the joint to stretch the capsule.



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