What are the causes of De Quervain's Tenosynovitis, particularly in women during pregnancy or after childbirth, and in individuals with occupations involving repetitive wrist and thumb motions?

Causes of De Quervain's Tenosynovitis

De Quervain's tenosynovitis is caused by repetitive loading that produces degenerative changes in the collagen fiber structure of the abductor pollicis longus (APL) and extensor pollicis brevis (EPB) tendons, not by acute inflammation. 1

Primary Pathophysiologic Mechanism

• The underlying pathology is degenerative tendinopathy (tendinosis) rather than inflammatory tendinitis—a critical distinction that affects both understanding and treatment approach 1
• Repetitive loading disrupts the normally highly organized collagen fiber structure of the APL and EPB tendons within the first dorsal compartment 1
• This degenerative process leads to non-inflammatory thickening of the tendinous sheath, causing entrapment of the individual tendons and increased friction 2

Mechanical and Occupational Risk Factors

• Repetitive wrist ulnar deviation combined with thumb abduction and extension is the classic mechanical cause 3
• Occupations or activities involving repetitive hand and thumb use are strongly associated with development of the condition 1
• A history of new activity or increased intensity of repetitive hand/thumb movements is common, though not universally present in all patients 1
• The condition can be associated with direct trauma, though most cases are of unknown specific etiology 2

Demographic and Hormonal Risk Factors

• Women are disproportionately affected, particularly those aged 30-50 years 2
• Pregnancy and the postpartum period (4-6 weeks after childbirth) represent significant risk periods for women 2
• The hormonal and biomechanical changes associated with pregnancy and caring for newborns (repetitive lifting, holding) likely contribute to this increased risk 2

Anatomical Predisposing Factors

• Subcompartmentalization within the first dorsal compartment can predispose individuals to the condition 1
• This anatomical variation affects both disease susceptibility and surgical outcomes if conservative management fails 1
• Ultrasound can detect these anatomical variations, including accessory tendons or septum within the first dorsal compartment 1

Important Differential Consideration

• When multiple tendons are symptomatic simultaneously, consider underlying rheumatic disease rather than isolated mechanical overuse 1
• Nontuberculous mycobacterial infections can cause tenosynovitis of the hand after direct inoculation through trauma, representing a distinct infectious etiology rather than the typical degenerative process 4, 1

Common Pitfall to Avoid

• Avoid mislabeling this condition as "tendinitis" when it represents degenerative tendinopathy ("tendinosis")—this misnomer can lead to inappropriate treatment strategies focused on inflammation rather than degenerative changes 1