Frozen Shoulder: Pathology, Anatomy, Exercise Program

Introduction

Frozen shoulder, also known as adhesive capsulitis, refers to a painful condition characterized by pain and progressive stiffness in the shoulder joint, leading to significant functional limitations. It affects about 2–5% of the general population, with increased prevalence in individuals aged 40–50 years and those with diabetes mellitus or thyroid disorders. This article examines the pathology of frozen shoulder, outlines physiotherapy evaluation techniques, and details a structured rehabilitation program, drawing on evidence from PubMed where relevant.

Pathology of Frozen Shoulder

Adhesive capsulitis involves inflammation and scarring of the glenohumeral joint capsule, resulting in restricted activeiterative and passive range of motion (ROM). The condition progresses through distinct stages, each with unique features characteristics.

Pathological Mechanisms

  1. Stages of Frozen Shoulder:
    • Stage 1 (Freezing/Painful Stage, 1–3 Months): Characterized by diffuse shoulder pain, especially at night, with mild ROM restrictions. Inflammation and capsular inflammation dominate, driven by inflammatory cytokines.
    • Stage 2 (Frozen/Stiffening Stage, 3–9 Months): Pain persists but stiffness becomes more pronounced, with significant ROM loss in multiple planes (e.g., external rotation, abduction). Capsular thickening and fibrosis develop, reducing joint volume.
    • Stage 3 (Thawing/Resolution Stage, 9–24 Months): Pain gradually subsides, and ROM slowly improves. Fibrotic tissue remodels, but full recovery may not occur in all cases.
  2. Histological Changes:
    • Early stages show synovial hyperplasia and increased vascularity, with elevated levels of inflammatory mediators (e.g., IL-1, TNF-α).
    • Later stages exhibit dense collagen deposition and fibroblast proliferation, leading to capsular contracture.
    • A PubMed study highlights the role of matrix metalloproteinases in tissue remodeling during the thawing phase.
  3. Pathophysiological Contributors:
    • Inflammation and Fibrosis: An initial inflammatory trigger (e.g., minor trauma, autoimmune response) leads to capsular inflammation, followed by fibrotic scarring.
    • Neurogenic Factors: Altered pain processing and sympathetic nervous system involvement may amplify symptoms.
    • Capsular Contracture: The axillary pouch and rotator interval are particularly affected, restricting glide and rotation of the humeral head.
  4. Risk Factors:
    • Systemic Conditions: Diabetes mellitus (10–20% prevalence in diabetics), thyroid disorders, and cardiovascular disease increase risk.
    • Demographic Factors: More common in women and middle-aged individuals.
    • Other Factors: Prolonged immobilization (e.g., post-surgery), trauma, or autoimmune conditions. A PubMed review notes a genetic predisposition in some populations.

Clinical Presentation

Patients typically present with:

Physiotherapy Evaluation

A comprehensive physiotherapy evaluation is essential to confirm the diagnosis, assess the stage of frozen shoulder, and guide treatment. The evaluation combines subjective and objective components.

Subjective Assessment

Objective Assessment

  1. Postural Analysis: Observe for compensatory postures (e.g., elevated shoulder, forward head) that may contribute to symptoms or indicate muscle imbalances.
  2. Range of Motion (ROM):
    • Measure active and passive ROM for flexion, abduction, external rotation, and internal rotation using a goniometer.
    • Frozen shoulder shows equal loss of active and passive ROM, with external rotation most restricted, followed by abduction and internal rotation (capsular pattern).
  3. Strength Testing: Assess rotator cuff and scapular stabilizer strength (e.g., deltoid, infraspinatus) to identify weakness due to disuse or pain inhibition. Manual muscle testing is performed cautiously to avoid exacerbation.
  4. Palpation: Identify tenderness around the glenohumeral joint, deltoid, or trapezius, and assess for muscle spasms or trigger points.
  5. Special Tests:
    • Empty Can Test or Hornblower’s Sign: To rule out rotator cuff pathology if weakness is present.
    • Apley’s Scratch Test: To assess functional ROM limitations.
    • Cervical Spine Screening: To exclude cervical radiculopathy or referred pain using Spurling’s test or upper limb tension tests.
  6. Functional Testing: Evaluate movement patterns during tasks like reaching overhead or behind the back to assess limitations and compensatory strategies.

Imaging and Correlation

Imaging is not routinely required but may be used to rule out differential diagnoses (e.g., rotator cuff tear, osteoarthritis). X-rays can identify calcific tendinitis or glenohumeral arthritis, while MRI or ultrasound may show capsular thickening or synovitis. A PubMed review emphasizes that clinical diagnosis, based on history and ROM restrictions, is sufficient in most cases, with imaging reserved for atypical presentations.

Rehabilitation Program

Physiotherapy is the cornerstone of frozen shoulder management, aiming to reduce pain, restore ROM, and improve function. The program is tailored to the disease stage, supported by PubMed evidence where applicable.

Phase 1: Pain Management and Gentle Mobilization (Freezing Stage, 0–3 Months)

Goals: Reduce pain, maintain available ROM, and prevent further stiffness.

Phase 2: Mobility Restoration (Frozen Stage, 3–9 Months)

Goals: Increase ROM, reduce capsular restrictions, and improve muscle strength.

Phase 3: Functional Restoration and Maintenance (Thawing Stage, 9+ Months)

Goals: Maximize ROM, restore strength, and return to full function.

Special Considerations

Conclusion

Frozen shoulder is a complex condition driven by capsular inflammation and fibrosis, leading to pain and significant ROM restrictions. Physiotherapy evaluation, combining subjective history, objective ROM assessment, and functional testing, guides stage-specific management. A structured rehabilitation program, emphasizing pain relief, mobility restoration, and functional training, is effective for most patients, supported by PubMed evidence. By addressing biomechanical and systemic factors, physiotherapy remains the cornerstone of treatment, improving outcomes and facilitating recovery in frozen shoulder.