What is calcific tendinopathy?

What is Calcific Tendinopathy?

Calcific tendinopathy is a disease characterized by the deposition of calcium hydroxyapatite crystals within tendons, most commonly affecting the rotator cuff of the shoulder, and represents a cell-mediated process rather than a simple inflammatory or degenerative condition. 1, 2, 3

Pathophysiology and Disease Process

Calcific tendinopathy is fundamentally different from typical overuse tendinopathies because it involves active calcium deposition rather than pure degenerative changes. 2, 3

• The condition involves multifocal, cell-mediated calcification of living tendon tissue, distinguishing it from simple calcium precipitation secondary to mechanical wear. 3
• Basic calcium phosphate (BCP) crystals, predominantly hydroxyapatite, are deposited within the tendon substance through an active cellular process. 1, 4
• The disease follows a predictable three-phase cycle: formative phase (calcium deposition), resting phase (stable deposits), and resorptive phase (spontaneous resorption). 5, 3

Clinical Presentation and Natural History

The clinical course varies dramatically depending on which phase the patient is experiencing:

• During the formative and resting phases, patients may be completely asymptomatic despite radiographic evidence of calcium deposits. 3
• The resorptive phase causes the most severe symptoms when calcium becomes soft, unstable, and undergoes phagocytosis, triggering intense local inflammation and pain. 5, 4
• The condition is self-limiting in most cases, with spontaneous resorption and tendon reconstitution occurring without intervention. 2, 3
• In a minority of cases, this self-healing process is disrupted, leading to persistent symptomatic disease requiring treatment. 2

Epidemiology and Common Locations

• The shoulder is the most prevalent location, specifically affecting the rotator cuff tendons, with the supraspinatus tendon being most commonly involved. 5, 6
• Reported prevalence ranges from 2.7% to 22% in various populations. 6
• The condition can occur in other tendons throughout the body, though less commonly than the shoulder. 4

Complications and Atypical Presentations

A critical pitfall is failing to recognize calcium migration patterns:

• During the resorptive phase, calcium deposits may migrate beyond the tendon into adjacent structures including bursae, bone, or muscle. 5, 4
• Intramuscular migration is particularly rare but causes significantly increased pain and functional limitation compared to typical presentations. 5
• Bursal migration is the most common atypical pattern, occurring when calcium extrudes from the tendon into the subacromial bursa. 4
• These atypical presentations create diagnostic dilemmas and can lead to unnecessary investigations if not recognized by radiologists and clinicians. 4

Distinction from Other Tendinopathies

Understanding what calcific tendinopathy is NOT is equally important:

• This is not a degenerative tendinosis with secondary calcium precipitation from mechanical overuse. 2, 3
• This is not primarily an inflammatory tendinitis, though inflammation occurs during the resorptive phase. 1
• The presence of calcium deposits distinguishes this from typical rotator cuff tendinopathy, which shows collagen disorientation and fiber separation without calcification. 1

Diagnostic Recognition

• Clinical diagnosis requires correlation of symptoms with the phase of disease visible on imaging. 3
• Radiographic, ultrasound, or CT imaging readily demonstrates the calcium deposits, with different appearances depending on disease phase. 1, 4
• The formative phase shows well-defined, dense calcifications, while the resorptive phase shows fluffy, ill-defined deposits. 3

Emerging Understanding

Recent evidence suggests calcific tendinopathy involves biological and genetic factors beyond simple mechanical theories, which may explain why current therapies provide only partially satisfactory outcomes in some patients. 2