Hemarthrosis  (effusion  of  blood  into  a  joint),  apart  from  injury,  may  be  due
to  a  number  of  causes  (sec  spontaneous  hemorrhage).  In  hemophilia,  follow-
ing a  slight  injury  or  sometimes  spontaneously,  a  joint  becomes  distended  with
blood,  which  may  gradually  be  absorbed,  leaving  the  joint  again  normal,  or
become  organized  and  lead  to  adhesions  and  obliteration  of  the  joint.  The
history  is  the  most  important  factor  in  diagnosis.  The  treatment  is  immobil-
ization and  compression.  Massage  and  passive  motion  may  be  used  with
caution  in  the  later  stages.    Under  no  circiunstances  should  the  joint  be  as-


AKKYXOSIS.
379


pirati-d  or  opened,  as  such  treatment  might  be  followed  by  uncontrollable
hemorrhage.
Loose  bodies  in  joints  (joint  mice)  consist  of  fibrin,  fatty  tissue,  fibrous
tissue,  cartilage,  or  bone.  Those  made  of  fibrin  are  usually  small  ami  numer-
ous, and  are  best  seen  in  tuberculosis  of  joints,  bursie,  or  tendon  sheaths  (rice
bodies).  Occasionally  they  are  due  to  other  causes,  e.g.,  a  small  foreign  body,
blood  clot,  or  detached  synovial  villus,  around  which  the  fibrin  collects.  Such
loose  bodies  frequendy  become  fibrous.  Bodies  which  are  at  first  pedun-
culated and  afterwards  become  loose  by  rupture  of  the  pedicle,  may  be  fatty
(in  lipoma  arborescens),  fibrous,  cartilaginous,  or  bony,  according  to  the  tis-
sue from  which  they  spring;  they  may  be  also  neoplasms,  or  result  from  hyper-
trophy of  sjTiovial  villi,  desiccation  of  cartilage,  or  detachment  of  osteophytes
in  chronic  arthritis.  The  most  frequent  cause,  however,  is  injury,  a  portion
of  bone,  or  more  frequently  cartilage,  being  detached  from  the  articular
surface,  usually  the  internal  condyle  of  the  knee,  which  is  the  joint  generally
affected.  Thou^  even  completely  detached,  these  bodies  may  continue  to
grow,  being  nourished  by  the  synovial  fluid.
