Hi. My name is***** Thank you for your question. I'm sorry to hear about Charlotte's situation with her ruptured cruciate ligament. I'll be honest and say that the ideal situation when one has this is surgical repair / stabilization of the knee affected to allow it to return to the best long term functional state. Surgery does have its down side as it has costs associated with it and there are times when there can be complications from it. So that is something that has to be taken into account anytime surgery is done. There are definitely cases where a ruptured cruciate ligament happens and the owners make the choice to not have surgery on it (due to costs, other factors like age of the pet, or other health issues). In these cases, the body does lay down scar tissue to try and stabilize the affected knee. They can get back some degree of function with it. When surgery isn't done, they will have arthritis develop in that knee and this is progressive. For some, it can be more significant than others. Here is a good link on the ruptured cruciate ligaments that I want you to read on.