Could be a weight problem. What size is she and how much does she weigh?
Or she may have joint problems Patellar Luxation which is graded 1 to 4 depending how loose the "loose knee" or sometimes "trick knee" is. It is somewhat common in small toy dogs like Chihuahuas usually starting about age 4-6.
Answered by HappyTrailChihuahua - 3/6/2013 1:57:52 AM