Frozen shoulder/ Adhesive Capsulitis

Functional Anatomy of the Glenohumeral Joint and Adhesive Capsulitis

The glenohumeral joint, often referred to as the shoulder joint, is one of the most mobile joints in the human body, but also one of the most unstable. This instability is due to the disparity in size between the humeral head and the glenoid cavity. The surface area of the humeral head is two to four times that of the glenoid, which is the shallow socket located on the scapula. Additionally, the humeral head has a diameter nearly double that of the glenoid when measured in the transverse plane.

This mismatch in size means there is limited articular contact between these structures, leading to an inherent instability within the joint. This lack of stability, however, is counteracted by a few key structures:

• Surrounding musculature, particularly the rotator cuff muscles, which help stabilise the joint during movement.
• The fibrocartilaginous labrum, a ring of cartilage that deepens the glenoid cavity and provides a more conforming surface for the humeral head.
• The shoulder capsule, a fibrous structure that encases the joint and offers support.

Despite these stabilising elements, the shoulder joint is still prone to various conditions, one of the most common being adhesive capsulitis, or frozen shoulder.

Understanding Adhesive Capsulitis

Adhesive capsulitis is a condition marked by stiffness and pain in the shoulder joint, resulting from the thickening and tightening of the glenohumeral capsule. This condition significantly reduces the range of motion, particularly external rotation, and can severely impact daily activities such as reaching overhead or behind the back.

Types of Adhesive Capsulitis

Adhesive capsulitis is typically divided into two categories:

• Primary (Idiopathic) Adhesive Capsulitis: This type develops spontaneously with no clear underlying cause. There is no apparent trauma or injury to the shoulder that triggers the onset.
• Secondary Adhesive Capsulitis: This type is more common and often develops in response to trauma or injury, such as fractures or dislocations, immobilisation of the upper extremity (e.g., following surgery), or abnormal shoulder mechanics resulting from overuse or poor posture.

Risk Factors and Associated Conditions

Although the exact cause of adhesive capsulitis remains unknown, research has shown that it is associated with several other medical conditions. Notably:

• Cervical spine disease, which affects the nerves that supply the shoulder, can lead to abnormal shoulder mechanics and inflammation.
• Diabetes mellitus, especially in individuals with poorly controlled blood sugar, is a known risk factor for adhesive capsulitis. Studies show that 6% of people with frozen shoulder also have diabetes.
• Rheumatoid arthritis and other autoimmune conditions that cause inflammation in the joints can also increase the likelihood of developing adhesive capsulitis.
• More serious conditions such as myocardial infarction (heart attack) and pulmonary cancer have been reported to have associations with adhesive capsulitis, although the exact mechanisms are unclear.

The condition most commonly affects individuals between the ages of 40 to 60, with a higher prevalence in women. Interestingly, it also seems to affect the left shoulder more frequently than the right, although the reasons behind this are not entirely understood.

Pathophysiology: What Causes Adhesive Capsulitis?

At a cellular level, adhesive capsulitis is characterised by fibrosis and thickening of the gleno-humeral capsule. This means that the normally pliable tissues of the capsule become stiff and inflamed, which restricts movement and causes pain. Over time, the capsule may also adhere to itself or to surrounding tissues, further limiting the range of motion.

The development of these changes typically progresses through three stages:

1. Freezing Stage: This is the initial phase where the shoulder becomes painful and progressively stiffer. The range of motion decreases as the inflammation increases. This phase can last from 6 weeks to 9 months.
2. Frozen Stage: During this stage, the shoulder may become less painful, but remains very stiff. The joint capsule has thickened, and adhesions may have formed. This phase can last from 4 to 12 months.
3. Thawing Stage: In this final phase, the shoulder slowly regains its range of motion, and the pain subsides. The thawing stage can last from 6 months to 2 years.

Self-Limiting Nature of Adhesive Capsulitis

One of the most frustrating aspects of adhesive capsulitis is its long duration, which averages around 2.5 years. However, the good news is that it is considered self-limiting, meaning the condition will eventually resolve on its own, with or without medical intervention. In some cases, treatment such as physical therapy, corticosteroid injections, or even manipulation under anaesthesia may be recommended to help relieve pain and restore mobility, but many patients recover fully without these interventions.

The primary concern during the course of the condition is the progressive loss of external rotation, which can severely limit the ability to perform routine tasks. However, as the thawing phase progresses, most people will regain the majority, if not all, of their shoulder function.

Other Conditions Associated with Adhesive Capsulitis

In addition to its associations with systemic diseases like diabetes and rheumatoid arthritis, adhesive capsulitis has also been linked to other conditions, such as:

• Cervical pain, with 25% of individuals reporting neck discomfort alongside frozen shoulder symptoms.
• Calcium deposits, which can occur in about 10% of cases and may contribute to stiffness and inflammation.
• Trauma or overuse injuries, which often precede the onset of secondary adhesive capsulitis.

Treatment and Management of Adhesive Capsulitis

While adhesive capsulitis is self-limiting, the pain and restricted movement can be debilitating. Treatment generally focuses on pain management and restoring range of motion. The most common treatment options include:

• Physical therapy: Gentle stretching exercises and range-of-motion exercises can help maintain or restore flexibility in the joint.
• Anti-inflammatory medications: Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen can help reduce pain and inflammation.
• Corticosteroid injections: These injections into the shoulder joint can help reduce inflammation and relieve pain, particularly in the freezing stage.
• Manipulation under anaesthesia: In severe cases, doctors may recommend manipulating the shoulder joint while the patient is under general anaesthesia to break up adhesions and restore movement.
• Surgical intervention: Although rare, some cases of adhesive capsulitis may require surgery to release the tight capsule and restore movement.

However, in most cases, patience and a tailored exercise regimen will lead to gradual improvement over time.

Conclusion

Adhesive capsulitis, though a painful and frustrating condition, will eventually resolve. Understanding its underlying causes, risk factors, and associations with other medical conditions can help patients manage their symptoms more effectively and seek appropriate treatment. While the recovery process can be long, with the right support and interventions, the shoulder’s range of motion can be restored, and normal function regained.