Thumb-base OA: prominence and "squaring" of the thumb base, due to osteophyte formation and subluxation at the first CMC joint.
OA: osteoarthritis; CMC: carpometacarpal.
Reproduced with permission from: OARSI Online Primer. Edited by Henrotin Y, Hunter D, Kawaguchi H. 2012. Osteoarthritis Research Society International. (http://primer.oarsi.org).
