This is one of those medical issues that is different for every dog and every owner. In our case, I had moved in my office chair, not knowing our chi mix was lying under it, and her foot became trapped by a wheel. In jerking away, Rosie yelped and tore her ACL. Our vet told us to crate or confine her for several weeks and the injury would probably would get better without surgery. That sounded good, but the dog soon told us different. Her eyes watered with pain and she was confused and upset at not being able to use her leg. Confining her only made it worse. We took her to a veterinary orthopedic surgeon who x-rayed it, checked her and over gave us our options. We opted for the surgery, and were never sorry. Rosie did develop a little arthritis in that leg after a few years, but never had a problem with the other ACL.