The surgeon I use for ortho surgery said that arthritis is not an issue with LP. The issue with LP is that after a period of time the cruciate ligament gets worn and often the pups end up tearing that ligament. With adult dogs he usually does not recommend surgery for LP because the ligament is already worn at that point and often the pup will end up tearing the ligament after the knee is repaired. Then, the poor pup must undergo another surgery and the owner is stuck with another large surgical bill. He does do repairs in young dogs to avoid all of the wear and tear. SO, I highly recommend you seek the opinion of an orthopedic surgeon. I personally will only use board certified surgeons. If interested you can find one at:
www.acvs.org Or, perhaps your vet knows of one.
Good luck and please keep us posted.