Hypothesis 2- Congenital


Congenital patellar luxation is a common stifle joint abnormality.  Medial luxation is 
more common in small breed dogs such as Pomeranians.  Many musculoskeletal 
abnormalities could cause this.  There is some defect in the extensor mechanism of the 
stifle:  quadrieps muscle group, the patella, the trochler groove, the patellar ligament, the 
tibial tuberosity.
Some abnormalities associated with medial patellar luxation:
-Coxa vera
-Lateral torsion of the femur
-Medial displacment of the quadriceps muscle group
-Lateral bowing of the distal one-third of the femur
-Shallow trochlear groove
-Dysplasia of the femoral epiphysis
-Rotational instability of the the stifle joint
-Tibial deformities
-Degenerative joint disease
-Shallow trochlear groove- lack opf normal pressure of the patella on the throchlear 
groove results in this

Dog is three years old Ð poossibly congenital defect was not seen until trauma occurred.