It is the most common reason a dog is sent to an orthopedic surgeon, and the first thing to know is that it is almost never an injury. Everything on this page is from the American College of Veterinary Surgeons, which is the body that certifies the specialist you are being referred to.
People call it a torn ACL, because that is the name of the same ligament in a human knee. In a dog it usually does not tear the way an athlete's does.
So the jump off the sofa was the moment it finally went, not the cause. It had been wearing for a while.
Any size, any breed, any age, and rarely cats. The ACVS lists the breeds that get it more often as the Rottweiler, Newfoundland, Staffordshire Terrier, Mastiff, Akita, Saint Bernard, Chesapeake Bay Retriever and Labrador Retriever, and the ones that get it less often as the Greyhound, Dachshund, Basset Hound and Old English Sheepdog.
The signs the ACVS lists, in their words: difficulty rising from a sit, difficulty in the process of sitting, trouble jumping into the car, decreased activity level or unwillingness to play, lameness of variable severity, sometimes only noted after long periods of rest, muscle atrophy in the affected leg, decreased range of motion of the knee, a popping or clicking noise, firm swelling on the inside of the shin bone, pain, and stiffness.
The clicking matters. The ACVS says it may indicate a meniscal tear. The meniscus is the cartilage pad inside the knee, and it can be damaged when the ligament goes.
The vet confirms it by hand. The knee moves in a way a stable knee cannot, which the ACVS calls the cranial drawer sign or tibial thrust.
This is the part nobody mentions in the consultation and everybody wishes they had known.
Elsewhere on the same page they put it at 40 to 60 percent at some future time. Either way, when you plan the money and the recovery for one knee, plan for the second one to be a coin toss.
The ACVS says strict activity restriction, meaning leash based activity only, is typically the most effective thing for reducing pain, and that rehabilitation may strengthen the muscles around the joint and can help delay surgery in dogs with partial tears. On custom knee braces, their line is that bracing is relatively new to canine orthopedics and there is little to go on about outcomes. Platelet rich plasma injections are listed as an option, made from the dog's own blood.
You will be quoted for one of these. They are the ACVS descriptions, shortened only where the sentence was about the cut rather than the outcome.
A semicircular cut around the top of the shin bone, which is then rotated to a set position. The ACVS says this procedure has consistent outcomes and the majority of dogs can go back to an active lifestyle after they have healed.
A straight cut along the front of the shin bone, and the front of the bone is moved forward to neutralize the forces around the knee.
A newer technique similar to the TPLO but with the cut in a different place. The ACVS says it is useful in young animals whose growth plates are still open.
A heavy suture placed outside the joint that mimics the ligament. The ACVS says this is often less costly, and that it may not be the best choice for larger and younger dogs because of the arthritic changes that follow.
A purpose made suture and toggle implants, placed through holes drilled in the thigh bone and the shin bone.
Several weeks of confinement, and the ACVS is blunt that this is to prevent complications with the implants and the healing bone. Rehabilitation starts immediately after surgery, and they say it can speed recovery and improve the final outcome whichever technique was used. It usually means passive range of motion, balance exercises and controlled walks on a leash.
Arthritis still comes, with or without surgery. The ACVS expects it to come more slowly when the knee has been operated on than when it has been managed without.
This page does not give a price. The ACVS does not, and the range you are quoted depends on the technique, the size of the dog, the practice and what the estimate includes. The one cost sentence the surgeons' college does offer is that the suture technique is often less costly.
The signs that a dog is in pain, with a checklist to tick before the visit: How do I know if my dog is in pain?