Diagnosis:  Congenital/Traumatic Medial Patella Luxation


	After interpreting the specialty exams, our final diagnosis is congenital/traumatic 
medial patella luxation.  (See interpretation)  Toy and miniature breed dogs, especially 
Pomeranians, have a high breed predilection for patella luxation.  We believe there is a 
combination of congenital and traumatic causes.  Titan may have been born with a 
shallow trochlear groove.  Therefore, when Titan jumped off the bed, the patella easily 
luxated medially from the shallow trochlear groove.  With this initial traumatic injury, 
symptoms develop slowly as cartilage is broken down. The dog was lame for a month 
following the injury; however, he stabilized his joint over time by the process of fibrosis.  
This would explain the medial buttressing noted on physical exam and justify the 
intermittent lameness.  Also, Titan could have suffered a fracture with this initial 
traumatic event.  Because the leg was never cast or stabilized, the femur could have 
healed incorrectly causing a lateral bowing of the distal one-third.  This was noted on the 
radiographs. Therefore, with these two predispositions, subsequent traumatic events, such 
as Òrough-housingÓ with the other household dogs, would cause a rapid onset of clinical 
signs as the patella reluxates.  This would account for the presentation of painful 
palpation and non-weight bearing lameness.