This past winter my European-line German shepherd, Zada, was diagnosed with luxating patellas. Dogs have "knees" much like we do. In their back legs, the ligament and patella (knee cap) on their legs fit into a sort of "groove" which is their knee joint. It's a fairly common knee joint affliction which can be caused by a traumatic injury or genetics.
When a dog has patellar luxation, the knee cap basically dislocates. While at first this isn't painful to the dog - unless caused by an injury - it does cause them to hold up a hind leg and hop along until the ligament/patella pops back into place (most often when the quadricep muscle relaxes/lengthens again). Over time, in ~50% of dogs this turns into an affliction of both hind legs. Also, the longer the dog lives with the condition, the worse it becomes as arthritis inevitably occurs as a result.
There are different 'Grade' levels for this disease, and while Zada is only a Grade I, she's also less than 3 years of age, and already showing the signs of patellar luxation, which is sure to become a chronic nuisance.
Also, since she displays the classic 'knock-kneed' stance associated with this affliction, and since there wasn't a traumatic injury, this makes me firmly believe it's an inherited condition; not an accident.
Numerous sites I used for reference for this post give the same warning:
"Keep in mind that patellar luxation is a heritable disease and we do not recommend breeding affected dogs. It is also very common for the disease to affect both legs." (Claws & Paws Veterinary Hospital)
"Patellar luxation should be considered an inherited disease." (OFA)
"...in the absence of trauma and breed predisposition supports the concept of patellar luxation resulting from a congenital or developmental misalignment of the entire extensor mechanism. Congenital patellar luxation is therefore no longer considered an isolated disease of the knee, but rather a component/consequence of a complex skeletal anomaly affecting the overall alignment of the limb, including:
- Abnormal conformation of the hip joint, such as hip dysplasia" (ACVS)