i had the operation done on a terrier of mine, you could flick his knee off from side to side, they repaired the ligament and put some false ligaments across the knee to hold it in place while it healed,i had to keep him kenneled for 10 weeks then walked on the lead for another 4 weeks,the first time i let him off the lead he came back limping it had gone again. the op cost me 300 quid 5 years ago i personaly wouldnt have it done on another dog but best of luck to you whatever you decide to do