In trigger finger the level of tendon sheath constriction is found at the level of:

Ans. is 'd' ie metacarpophalangeal joint (Ref: Adam's outline of orthopedics, 13/e, p291; Apley's, 8/e, p344).Adams states - "In this rather common condition thickening and constriction of the mouth of a fibrous digital sheath interfere with the free gliding of the contained flexor tendons."The mouth of the fibrous digital sheath is at the level of metacarpo-phalangeal joint.Trigger finger (Stenosing tenovaginitis)As stated above this condition result from constriction of the fibrous digital sheath at the entrance, so that the free gliding of contained flexor tendons does not occur.Although any digit (including thumb) may be affected, but the ring and middle fingers are most commonly affected.Initially the only symptoms is pain at the base of the affected finger.As the sheath further thickens, the contained tendon gets swollen proximal to it. The swollen segment of tendon does not enter the sheath when an attempt is made to straighten the finger from the flexed position. This is called locking of the finger. This locking can be overcome either by a strong effort in which case the finger extends with a snap-like trigger of a pistol.TreatmentEarly cases may be caused by injection of methylprednisolone carefully placed into the tendon sheath. Refractory cases need operation - incision of the fibrous sheath.