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MP Joint Locking


- Discussion:
    - index finger is most commonly involved, often found in older pts w/degenerative arthritis;
- Etiology:
    - muscular contracture or trauma;
    - collateral ligament or volar plate tethering on prominent MP head or osteophyte (on either side or volar aspect of metacarpal head);
    - torn palmar plate;
    - metacarpal head fracture;
    - loose body
    - abnormal sesamoids
- Diff Dx:
    - must be differentiated from Trigger Finger which is caused by stenosis of flexor tendon sheath in region of A1 pulley;
         - in Trigger Finger, catching characteristically occurs in PIP joint, where w/ "MP Locking", locking is in MP joint;
- Exam:
    - on exam, flexor tendons are intact, & active finger flexion may be nearly normal;
    - MP joint may not allow extension past  40 to 50 deg of MP flexion;
    - attempts to straighten the digit are painful;
- X-ray:
    - consider oblique x-rays of hand to demonstrate bony osteophyte


Locking of the metacarpophalangeal joint of the thumb.