Most common cause of trigger finger -

Trigger finger resulting from constriction of fibrous digital sheath, so that free gliding of the contained flexor tendon does not occur.The underlying cause is unknown but the condition is ceainly more common in patients with diabetes. People with rheumatoid disease may develop synol thickening or intratendinous nodules which can also cause triggering. Occupational factors, though sometimes blamed, are unlikely to be causative. Reference- Apley&;s system of ohopaedics 9th edn- pg no 423.