L iving ▁people ▁Category : Mus icians ▁from ▁Louis ville , ▁Kentucky ▁Category : D u P ont ▁Man ual ▁High ▁School ▁al umn i <0x0A> </s> ▁Ext ensor ▁dig itor um ▁bre vis ▁manus ▁is ▁an ▁extra ▁or ▁access ory ▁mus cle ▁on ▁the ▁back side ▁( d ors um ) ▁of ▁the ▁hand . ▁It ▁was ▁first ▁described ▁by ▁Al bin us ▁in ▁ 1 7 5 8 . ▁The ▁mus cles ▁lies ▁in ▁the ▁fourth ▁ext ensor ▁compart ment ▁of ▁the ▁w rist , ▁and ▁is ▁relatively ▁rare . ▁ ▁It ▁has ▁a ▁pre val ence ▁of ▁ 4 % ▁in ▁the ▁general ▁population ▁according ▁to ▁a ▁meta - analysis . ▁This ▁mus cle ▁is ▁commonly ▁mis di agn osed ▁as ▁a ▁gang l ion ▁c yst a , ▁syn ov ial ▁nod ule ▁or ▁c yst . ▁ ▁Str ucture ▁ ▁The ▁ext ensor ▁dig itor um ▁bre vis ▁manus ▁usually ▁origin ates ▁from ▁the ▁d ors al ▁aspect ▁( back side ) ▁of ▁the ▁w rist , ▁either ▁from ▁the ▁joint ▁caps ule , ▁the ▁dist al ▁end ▁( the ▁most ▁distant ▁end ) ▁of ▁the ▁radius , ▁the ▁met ac arp al , ▁or ▁from ▁the ▁radi oc arp al ▁lig ament ▁in ▁the ▁area ▁of ▁the ▁fourth ▁ext ensor ▁compart ment . ▁Many ▁variations ▁of ▁the ▁mus cle ▁have ▁been ▁described ▁in ▁the ▁literature . ▁It ▁could ▁have ▁up ▁to ▁four ▁tend ons ▁with ▁a ▁single ▁tend on ▁inserting ▁to ▁the ▁index ▁or ▁the ▁middle ▁finger