Definition
Stenosing tenosynovitis of the flexor tendon sheath. A size mismatch between the flexor tendons and the A1 pulley causes painful catching and locking of the digit.
Aetiology
- Thickening and fibrocartilaginous metaplasia of the A1 pulley
- Diabetes mellitus, with more digits involved and a poorer response to injection
- Rheumatoid arthritis, hypothyroidism, amyloidosis and chronic renal disease
- Coexists with carpal tunnel syndrome, de Quervain’s and Dupuytren’s disease
Epidemiology
- Lifetime risk about 2 to 3%, and up to 10% in diabetes
- Women in the fifth and sixth decades
- Ring finger and thumb most often affected
Anatomy
- A1 pulley lies over the MCP joint at the distal palmar crease
- Radial digital nerve of the thumb crosses obliquely close to the thumb A1 pulley
Classification
- Green grading, a modification of Quinnell
- Grade I. Pain and A1 pulley tenderness without triggering
- Grade II. Catching, with active extension still possible
- Grade IIIA. Locking that needs passive extension
- Grade IIIB. Inability to flex the digit fully
- Grade IV. Fixed flexion contracture of the PIP joint
Clinical Features
- Painful clicking or locking, worse in the morning
- Symptoms often felt at the PIP joint
- Tender palpable nodule over the A1 pulley
- Triggering reproduced on active flexion and extension
Investigations
- Clinical diagnosis
- Ultrasound shows pulley thickening and sheath fluid in atypical cases
Differential Diagnosis
- Dupuytren’s disease
- MCP joint locking from volar plate or collateral ligament entrapment
- Flexor tendon sheath ganglion
- Sagittal band rupture with extensor tendon subluxation
Management
- Splinting. MCP joint blocking splint for 6 to 10 weeks in mild disease
- Corticosteroid injection. Resolves most non-diabetic digits, with recurrence after one or two injections common
- Open A1 pulley release. Lower recurrence than injection, see Trigger Finger Release
- Percutaneous release. Results similar to open release, with a risk of digital nerve injury
- Rheumatoid digits. Flexor tenosynovectomy with A1 pulley preservation to avoid ulnar drift
Complications
- Bowstringing if the A2 pulley is divided
- Digital nerve injury, most often the radial digital nerve of the thumb
- Recurrence and persistent PIP joint contracture
References
- Makkouk AH, Oetgen ME, Swigart CR, Dodds SD. Trigger finger. Etiology, evaluation, and treatment. Curr Rev Musculoskelet Med. 2008, 1(2), 92-6. PubMed
- Fiorini HJ, Tamaoki MJ, Lenza M, Gomes Dos Santos JB, Faloppa F, Belloti JC. Surgery for trigger finger. Cochrane Database Syst Rev. 2018, 2(2), CD009860. PubMed
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 19 October 2026.