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Cruciate Ligament Tears in Dogs (CCL or ACL)

Cruciate ligament disease is the most common cause of back-leg lameness in dogs. The signs, surgery options like TPLO, recovery time and the risk to the other knee.

Updated October 2026 · 7 min read · By the Hushku editorial team · 1 sources

Short answer

The cranial cruciate ligament (the dog equivalent of the human ACL) stabilises the knee. In dogs it usually weakens gradually and then tears, causing back-leg lameness, difficulty sitting and rising, and stiffness after rest. Surgery such as TPLO is generally the best way to stabilise the knee, with significant improvement in 85–90% of dogs. 40–60% of affected dogs later develop the same problem in the other knee.

Key facts

Most tears follow slow degeneration of the ligament, not sudden injury.
Partial tears almost always progress to full tears.
Surgery gives significant improvement in 85–90% of dogs.
40–60% of dogs later develop it in the other knee.

Definition

Cranial cruciate ligament disease (CCLD) is degeneration and tearing of the ligament that stops the shinbone (tibia) sliding forward relative to the thigh bone (femur), leaving the knee unstable.

Unlike in people, where ACL tears are usually sports injuries, the American College of Veterinary Surgeons explains that most canine cruciate ruptures result from slow degeneration of the ligament over time, influenced by age, obesity, fitness, genetics, conformation and breed. Partial tears almost always progress to full tears.

Breeds with a higher risk include Rottweilers, Newfoundlands, Staffordshire Terriers, Mastiffs, Akitas, Saint Bernards, Chesapeake Bay Retrievers and Labradors. It's rare in cats.

When the ligament tears, the knee becomes unstable, which causes pain, inflammation and, over time, arthritis. The meniscus, a cartilage cushion in the knee, is often damaged too.

Signs and symptoms

Lameness in a back leg, sudden or gradually worsening
Sitting with the affected leg stuck out to the side (a positive 'sit test')
Difficulty rising, jumping into the car or climbing stairs
Stiffness after rest, improving with gentle movement
Muscle loss in the thigh
A clicking sound when walking, which can mean a torn meniscus
A firm swelling on the inside of the knee

Causes and risk factors

Gradual degeneration of the ligament
Being overweight or unfit
Breed and genetics
Leg conformation, such as a steep tibial plateau
Less often, a sudden injury

Treatment

TPLO (tibial plateau levelling osteotomy): the shinbone is cut and rotated so the knee is stable without the ligament; most dogs return to active lives
TTA (tibial tuberosity advancement): an alternative bone-cutting procedure
Extracapsular suture: a lower-cost option, generally better suited to smaller, less active dogs
Conservative care: pain relief, strict activity restriction, weight loss, rehabilitation and sometimes a custom brace

Prevention

Keep your dog at a healthy weight; obesity is a major risk factor
Regular, consistent exercise rather than 'weekend warrior' bursts
Build fitness gradually in young and large-breed dogs

Diagnosis

Vets usually diagnose cruciate disease by feeling for abnormal movement in the knee (the 'cranial drawer' or 'tibial thrust' tests), sometimes under sedation for partial tears. X-rays are used to plan surgery and assess arthritis.

Recovery

After surgery, activity is restricted for several weeks while the bone heals, with short lead walks only. ACVS advises starting rehabilitation straight after surgery, as it speeds recovery and improves outcomes. Most dogs return to normal activity within a few months.

The other knee

ACVS notes that 40–60% of dogs with cruciate disease in one knee eventually develop it in the other, often within a year or two. Keeping your dog lean and fit is one of the best ways to reduce that risk.

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Sources

ACVS: Cranial cruciate ligament disease

We check guides against veterinary sources and update them when guidance changes. How we write and review.

Questions.

Can a dog's cruciate ligament heal on its own?

The ligament doesn't heal, but scar tissue can partly stabilise the knee over months, especially in small dogs. Arthritis usually progresses, so surgery is generally recommended for larger and active dogs.

Is TPLO better than other surgeries?

TPLO is widely used and has good outcomes, especially in medium to large active dogs. The best option depends on your dog's size, age, activity and your surgeon's advice.

How do I know if my dog tore its ACL?

Sudden back-leg lameness, especially after exercise, and sitting with the leg out to the side are common signs. A vet exam confirms it.