2diagnosis_a.txt.  

Our diagnosis is congenital medial luxation of the patella, a condition that is fairly common in small breed dogs. Initially, the lameness is due to lack of stability in the stifle joint. The luxation is thought to be due to misalignment of the extensor mechanism of the stifle joint (problems with one or more of the following: quadriceps muscle group, patella, a shallow trochlear groove, straight patellar ligament, or rotational instability of the stifle joint.)  During the dog's development, these deformities can cause abnormal forces on the growth plates.  In this dog no long bone deformities were noted on radiographs, suggesting that the lameness is only due to the patellar luxation.  Dogs can sometimes learn how to pop the patella back into place, causing resolution of the lameness (explaining the intermittent nature of this lameness).  
	It is important to correct the luxation to prevent progression to degenerative joint disease.  Chronic medial luxation can cause erosion to the articular cartilage, inflammation of the joint capsule, and potentially bone remodeling.