Causes of Trigger Finger (Locked Finger)
Trigger finger is caused by inflammation and narrowing of the A1 pulley, which creates a stenotic environment that loses its gliding surface, producing friction and nodular changes in the flexor tendon. 1, 2
Primary Pathophysiology
The fundamental mechanism involves:
- Stenosing flexor tenosynovitis where the A1 pulley becomes narrowed and stenotic, impairing smooth movement of the finger flexor tendon through this pulley 1, 3
- Loss of the gliding surface within the A1 pulley, which generates friction between the tendon and pulley 2
- Nodular thickening develops in the tendon itself as a result of this chronic friction and inflammation 2
- Degeneration, inflammation, and swelling of the tendon-pulley interface that progressively restricts tendon excursion 4
Clinical Progression
The pathologic process follows a predictable sequence:
- Initial stage: Pain and tenderness to palpation directly over the A1 pulley 2
- Intermediate stage: Catching sensation as the nodular tendon struggles to pass through the narrowed pulley 2
- Advanced stage: Complete locking where the finger becomes stuck in flexion and cannot extend without manual assistance 2
Risk Factors and Epidemiology
Certain populations are at substantially higher risk:
- Diabetic patients have significantly increased incidence and are at higher risk for treatment failure with conservative measures 1, 2
- Women in the fifth to sixth decade of life (ages 50-60 years) represent the most commonly affected demographic 1
- Patients with multiple trigger fingers are more likely to experience recurrent symptoms and injection failure 2
Important Clinical Caveat
While the diagnosis is typically straightforward based on the characteristic clicking or locking symptoms, other pathological processes must be excluded, including fractures, tumors, or other traumatic soft tissue injuries that can mimic trigger finger presentation 1. This is particularly important in patients presenting after trauma or with atypical symptoms.