What are the risk factors, pathophysiology, and structures involved in Adhesive Capsulitis (frozen shoulder)?

Adhesive Capsulitis: Risk Factors, Pathophysiology, and Structures Involved

Risk Factors

Adhesive capsulitis predominantly affects individuals aged 40-65 years, with diabetes and thyroid disorders representing the most significant systemic risk factors. 1, 2

Patient Demographics and Systemic Conditions

• Age: Most commonly occurs between 40-65 years of age 1, 2
• Diabetes mellitus: Strong association with adhesive capsulitis development 2
• Thyroid disease: Established risk factor for frozen shoulder 2
• Combined motor, sensory, and visuoperceptual deficits in stroke patients: Up to 67% incidence of shoulder-hand-pain syndrome in this population 3

Post-Stroke Specific Risk Factors

• Improper handling during rehabilitation: Particularly overhead pulley exercises that encourage uncontrolled abduction 4
• Shoulder tissue injury: Approximately one-third of acute stroke patients show ultrasound evidence of effusion, tendinopathy, or rotator cuff tears that may contribute to capsulitis 4
• Spasticity: Correlates with development of shoulder complications, though definitive causation remains unconfirmed 4
• Inadequate protection of hemiplegic limb: Failure to prevent trauma increases risk 4

Pathophysiology

The pathophysiology of adhesive capsulitis remains poorly understood but involves progressive fibrosis and contracture of the glenohumeral joint capsule, leading to characteristic restriction of both active and passive range of motion. 5

Structural Changes

• Capsular fibrosis and contracture: The hallmark pathological change affecting the glenohumeral joint capsule 5
• Inflammatory component: Early stages involve pain and inflammation, though the exact mechanism is unknown 2
• Sympathetic dysregulation: Proposed role in some patients, particularly those with predominant sympathetic nervous system hyperactivity, though its central importance is debated 4

Clinical Stages

The condition progresses through three distinct phases 5, 6, 7:

1. Freezing (Painful) Stage: Characterized by progressive pain and beginning loss of motion
2. Frozen (Adhesive) Stage: Marked by stiffness with reduced pain but severely restricted range of motion
3. Thawing Stage: Gradual recovery of motion, though many patients never fully recover 5

Diagnostic Findings

• Bone scintigraphy: Demonstrates increased periarticular activity in adhesive capsulitis 8
• Triple phase bone scan: Shows increased periarticular uptake in distal upper extremity joints when shoulder-hand syndrome is present 4

Structures Involved

The primary structure affected is the glenohumeral joint capsule, with particular involvement of the rotator interval and axillary recess. 5

Primary Anatomical Structures

• Glenohumeral joint capsule: The main structure undergoing fibrosis and contracture 5
• Rotator interval: Area between supraspinatus and subscapularis tendons, commonly involved in capsular thickening
• Axillary recess: Typically shows significant contracture and loss of volume

Range of Motion Limitations

• External (lateral) rotation: Most significantly affected and relates most strongly to onset of shoulder pain 3
• Abduction: Severely restricted in frozen stage 3, 7
• Internal rotation: Often the most difficult motion to recover, particularly in phase 2 disease 7
• Extension: May remain limited even after treatment 7

Associated Structures in Post-Stroke Patients

• Metacarpophalangeal and proximal interphalangeal joints: When shoulder-hand syndrome develops, these joints show pain, tenderness, and edema 4
• Subacromial region: May be involved when pain relates to injury or inflammation of this area 4
• Subscapularis and pectoralis muscles: Can contribute to pain when spasticity is present 4

Clinical Impact and Complications

Adhesive capsulitis can delay rehabilitation and functional recovery, particularly in stroke patients, where it may mask motor function improvement or inhibit use of assistive devices. 3, 8

Functional Consequences

• Delayed rehabilitation: Pain limits participation in therapy and use of canes or wheelchairs for ambulation 3
• Depression and sleeplessness: Contributes to reduced quality of life 8
• Incomplete recovery: Many patients experience residual effects even after the thawing phase 5, 2

Common Pitfalls to Avoid

• Overhead pulley exercises: These encourage uncontrolled abduction and dramatically increase risk of hemiplegic shoulder pain; should be avoided 3, 4
• Inadequate staff education: Failure to train healthcare providers on proper handling of the hemiplegic shoulder allows preventable trauma 4
• Delayed intervention: Early diagnosis and treatment, particularly before phase 2 when range of motion becomes completely reduced, yields better outcomes 7