Ulnar deviation
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Ulnar deviation, also known as ulnar drift, is a hand deformity in which the swelling of the metacarpophalangeal joints (the big knuckles at the base of the fingers) causes the fingers to become displaced, tending towards the little finger.{{Citation |last=Strike |first=Sophia A. |title=Chapter 14 - Closed Reduction Forearm and Wrist (Adult) |date=2017-01-01 |work=Case Competencies in Orthopaedic Surgery |pages=131–137 |editor-last=Frank |editor-first=Rachel M. |url=https://www.sciencedirect.com/science/article/pii/B9780323390385000147 |access-date=2024-02-02 |publisher=Elsevier |doi=10.1016/b978-0-323-39038-5.00014-7 |isbn=978-0-323-39038-5 |last2=LaPorte |first2=Dawn M. |editor2-last=Forsythe |editor2-first=Brian |editor3-last=Provencher |editor3-first=Matthew T.|url-access=subscription }} Its name comes from the displacement toward the ulna (as opposed to radial deviation, in which fingers are displaced toward the radius). Ulnar deviation is likely to be a characteristic of rheumatoid arthritis,{{Citation |last=Biese |first=JEANINE |title=Chapter 17 - Arthritis |date=2007-01-01 |work=Fundamentals of Hand Therapy |pages=348–375 |editor-last=Cooper |editor-first=Cynthia |url=https://www.sciencedirect.com/science/article/pii/B0323033865500205 |access-date=2024-02-02 |place=Saint Louis |publisher=Mosby |doi=10.1016/b0-32-303386-5/50020-5 |isbn=978-0-323-03386-2|url-access=subscription }} more than of osteoarthritis. Consideration should also be given to pigmented villonodular synovitis, in the setting of ulnar deviation and metacarpophalangeal synovitis. {{citation needed|date=February 2024}}
Ulnar deviation is also a physiological movement of the wrist, where the hand including the fingers move towards the ulna.
Ulnar deviation is a disorder in which flexion by ulnar nerve innervated muscles is intact while flexion on the median nerve side is not.{{citation needed|date=February 2024}}