Glossary

Cruciate ligament tear

A tear of the cranial cruciate ligament, the main stabilizer of the dog's knee, and a leading cause of sudden hind-leg lameness.

Also called: CCL tear, CCL rupture, ACL tear in dogs, torn knee ligament, cranial cruciate ligament rupture

The cranial cruciate ligament, or CCL, is the dog version of the human ACL. It stops the shin bone sliding forward on the thigh bone. When it tears, the knee becomes unstable, and a dog may suddenly hold up a hind leg, sit with the leg sticking out sideways or limp after exercise.

In dogs the ligament often weakens gradually from degeneration before it finally gives way, which is why it frequently happens during ordinary play and why many dogs tear the second knee later. Overweight dogs and breeds such as the Labrador Retriever and Rottweiler are overrepresented.

A vet confirms it by feeling the knee and sometimes with X-rays. Treatment options depend on the dog's size and age, so ask a veterinarian rather than resting a limping dog for weeks.

Last reviewed November 8, 2026

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Related terms

Luxating patella A condition in which the kneecap slips out of its groove, common in small breeds and often seen as a brief hop or skip in the stride. Osteoarthritis A long-term, painful wearing down of joint cartilage that causes stiffness and reluctance to move, common in older and overweight dogs. Obesity Excess body fat that shortens lives and raises the risk of arthritis, diabetes and other disease; it is the most common nutrition problem in pet dogs.