Although the luxation may not be present at birth, the anatomical deformities that cause these luxations are present at that time and are responsible for subsequent recurrent patellar luxation. Patellar luxation in these breeds should be considered an inherited disease. Neonates and older puppies often show clinical signs of abnormal hind-leg carriage and function from the time they start walking, these present grades 3 and 4 generally. 2.Young to mature animals with grade 2 to 3 luxations usually have exhibited abnormal or intermittently abnormal gaits all their lives but are presented when the problem symptomatically worsens. Older animals with grade 1 or 2 luxations may exhibit sudden signs of lameness because of further breakdown of soft tissues as result of minor trauma, or because of worsening of degenerative joint disease pain.
Signs vary dramatically with the degree of luxation.
In grades 1 and 2, lameness is evident only when the patella is in the luxated position. The leg is carried with the stifle joint flexed, but may be touched to the ground every third or fourth step. The heritability is unknown. Skeletal abnormalities are relatively minor in this syndrome, which seems to represent a breakdown in soft tissue in response to, as yet, obscure skeletal derangement. Thus, most lateral luxations are grades 1 and 2, and the bony changes are similar, but opposite to those described for medial luxation.