Hypothesis 2: Congenital

Patellar luxation pre-existed in both stifles (Congenital problem is common in 
Pomeranians and medial luxation is more common in Pomeranians),  left originally worse 
than right, so right leg was used to compensate and bear more weight.  The extra weight 
and heavy usage of the right leg over the left eventually led to right leg lameness.  If the 
trauma of jumping off the bed played a role in developing the lameness in the right leg, it 
is probably due to the dog landing on the right leg hard in order to avoid further pain in 
the left leg.  The fact that the patellar luxation existed previously in the right leg makes 
the leg more sensitive to overuse.  There may be a cranial cruciate ligament rupture in the 
left stifle which is also contributing to the overuse of the right leg, leading to further 
lameness of the right hind leg.  Another possibility is congenital malpositioning of the quadriceps muscle which would allow more movement of the patella.