Cause of Trigger Finger
Trigger finger is caused by inflammation and narrowing of the A1 pulley, creating a size mismatch between the flexor tendon and the pulley through which it glides, resulting in mechanical catching and locking of the affected digit. 1, 2
Primary Pathophysiology
The fundamental mechanism involves stenosing tenosynovitis—a condition where the flexor tendon becomes too large relative to the A1 pulley opening. 2 This size discrepancy prevents smooth gliding of the tendon during finger flexion and extension, producing the characteristic clicking, catching, and locking symptoms. 1
The inflammation occurs specifically at the A1 pulley level, which is the first annular pulley of the flexor tendon sheath located at the metacarpophalangeal joint. 2 As inflammation progresses, the pulley narrows further while the tendon may develop nodular thickening, exacerbating the mechanical obstruction. 1
Risk Factors and Associated Conditions
Demographic Patterns
- Women are affected more frequently than men, typically presenting in the fifth to sixth decade of life. 1
- Middle-aged women represent the highest risk demographic group. 3
- The thumb is the most commonly involved digit, followed by other fingers. 3
Medical Comorbidities
- Diabetes mellitus is strongly associated with trigger finger and shows less responsiveness to conservative treatment measures. 3, 2
- Carpal tunnel syndrome frequently coexists with trigger finger. 3
- Rheumatoid arthritis patients develop trigger finger through a different mechanism requiring tenosynovectomy rather than simple A1 pulley release. 2
Mechanical Factors
- Repetitive finger movements contribute to development through cumulative microtrauma and inflammation. 3
- Occupational activities involving repetitive gripping or forceful hand use increase risk. 3
Clinical Pitfalls
A critical distinction must be made: trigger finger is fundamentally a mechanical problem with inflammatory components, not primarily an inflammatory disease. 3 This understanding guides treatment selection—addressing the mechanical obstruction (through splinting, injection, or surgical release) rather than treating inflammation alone. 1
In pediatric populations, trigger thumb resolves reliably with A1 pulley release, but other digits may require more extensive surgical intervention, indicating different underlying pathomechanics in children. 2
Diabetic patients warrant special consideration as their trigger finger demonstrates reduced response to conservative measures including corticosteroid injections, often necessitating earlier surgical intervention. 2