Unfortunately Kluf, my buddy Rocco tore his ACL early last summer in his right leg. Vet told us the surgery would most likely lead to arthritis in his other leg due to not being able to use the operated on leg. He is 7. He had recovered to about 90% and then late last year, he injured his left rear leg. The vet did not check him out on that one, but my concern is that he has since torn both. Poor guy has been limping ever since. He still goes all out when we are playing and running, but he pays for it afterwards.