Cruciate ligament rupture
Tearing of the cranial cruciate ligament in the knee. The most common orthopaedic injury in dogs. Often surgical.
The cranial cruciate ligament (the dog equivalent of the human ACL) stabilises the knee. In dogs it usually tears not from a single trauma but from chronic degeneration — and once one knee tears, the other often follows within 12–18 months.
Risk factors: breed (Labradors, Rottweilers, Golden Retrievers, Bulldogs, Newfoundlands), obesity, early-age neutering in large breeds, conformation. Signs: sudden hindleg lameness, hesitation to bear weight on the affected leg, often partial improvement over a few days then persistent intermittent lameness, sometimes a clicking sound.
Treatment is usually surgical for medium and large dogs — most commonly tibial plateau levelling osteotomy (TPLO) or tibial tuberosity advancement (TTA). Small dogs may do well with extracapsular repair or conservative management.
Surgical recovery is 3–4 months of strictly restricted activity. Most dogs return to near-normal function. Without surgery, larger dogs develop chronic lameness and severe arthritis.
In cats, cruciate rupture is much less common.