Cranial Cruciate Ligament (CCL) disease concerns tears and ruptures of the knee ligament.  At first we thought these might be associated with luxating patellas (which may contribute) or with poor rear angulation conformation.  However, one cause may be associated with the increased number of Border Terriers participating in Agility and similar high impact activities.  Weekend Warrior syndrome can occur in dogs as well as in humans.  It is important that dogs participating in high impact and acute turning sports be properly conditioned.   Luxating patellas are familial in some breeds but we do not have evidence at this time to support that in Border Terriers.   The same applies to dogs with CCL disease.