This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bony dysplasia and soft tissue affection, Subject name: Orthopaedics
[{'content': 'In trigger finger the level of tendon sheath constriction is found at the level of - \nSelect and explain. \nA. Middle phalanx, B. Proximal interphalangeal joint, C. Proximal phalanx, D. Metecarpophalangeal joint', 'role': 'user'}, {'content': "Answer: D \nExplanation: TRIGGER FINGER (DIGITAL TENOVAGINOSIS) A flexor tendon may become trapped by thickening at the entrance to its sheath; on forced extension it passes the constriction with a snap ('triggering'). Clinical features ,Any digit may be affected, but the thumb, ring and middle fingers most commonly; sometimes several fingers are affected. The patient notices a click as the finger is flexed; when the hand is unclenched, the affected finger initially remains bent at the PIP joint but with fuher effo it suddenly straightens with a snap. A tender nodule can be felt in front of the MCP joint and the click may be reproduced at this site by alternately flexing and extending the finger. Reference- Apley&;s system of ohopaedics 9th edn-pg no 423", 'role': 'assistant'}]