[Smokey]

Here's a good article on cruciate ligament injury in dogs. My dog Annabelle injured one knee chasing a tennis ball, then the other two years later chasing a squirrel. She had the TPLO surgery the last time. It effectively ended her hiking but she would be crippled without the surgeries. Spendy, another reason to think about whether or not you want a dog. It's a fairly common injury, amongst the dog owners I know anyway. Cruciate ligament injury in dogs