The cranial cruciate ligament sits inside the stifle — the dog’s knee — and stops the shin bone sliding forward relative to the thigh bone. When it fails, the joint becomes unstable, and every step causes abnormal movement, inflammation and eventually arthritis.
It is the most common orthopaedic injury vets see.
It is usually not an injury
This is the part that surprises owners. In humans, a cruciate tear is typically a sudden traumatic event on a sports pitch.
In dogs, the ligament usually degenerates over months or years and then fails during something ordinary — jumping off the sofa, turning at speed, or slipping on a floor. The trigger looks like the cause, but the ligament was already compromised.
That has two consequences:
- It is often bilateral. Studies suggest a substantial proportion — commonly quoted as around 40 to 60 percent — of dogs who rupture one cruciate will rupture the other, frequently within a year or two
- The other knee is already changing, which is why vets examine both
Risk factors
- Body weight. The largest modifiable factor by a clear margin
- Breed. Labradors, Rottweilers, Newfoundlands, Staffordshire Bull Terriers, Boxers, West Highland White Terriers and Bichons are over-represented
- Neutering, particularly early neutering in some large breeds, which several studies associate with increased risk
- Conformation, including a steep tibial plateau angle
- Poor fitness with occasional intense activity — the weekend-warrior pattern
- Age — most cases occur in middle age
Signs
Complete rupture: sudden hind limb lameness, often non-weight-bearing initially, frequently after a turn or a jump.
Partial tear: intermittent lameness that improves with rest and returns with exercise. This is the one that gets missed for months.
Other signs:
- Sitting with the affected leg kicked out to the side rather than tucked under. This is a very characteristic sign
- Difficulty rising
- Stiffness after rest
- Muscle loss on the affected thigh over weeks
- A clicking sound from the joint, which can indicate a torn meniscus
- Reluctance to jump or use stairs
Diagnosis
Physical examination, checking for joint instability with the cranial drawer and tibial compression tests. Tense dogs can mask instability, so sedation is often needed for a reliable assessment.
X-rays show joint swelling and arthritis, and rule out other causes. The meniscus — a cartilage cushion in the joint, which is damaged in a substantial proportion of cases — is usually assessed at surgery.
Treatment
For most medium and large dogs, surgery gives the best outcome. Conservative management is more reasonable in small dogs under about 15kg, though outcomes are still generally better with surgery.
The main options:
TPLO (tibial plateau levelling osteotomy). The tibia is cut and rotated to change the angle of the joint surface, so the shin no longer wants to slide forward. This makes the ligament unnecessary rather than replacing it. The most common procedure for medium and large dogs, with good published outcomes.
TTA (tibial tuberosity advancement). A related principle, altering the mechanics via the patellar tendon.
Extracapsular repair (lateral suture). A heavy suture outside the joint stabilises it while scar tissue forms. Less invasive, cheaper, and generally reserved for smaller and less active dogs.
Your surgeon will recommend based on size, age, activity, conformation and cost. All three work; the evidence generally favours the osteotomy procedures in larger dogs.
Conservative management — strict rest, pain relief, weight loss and physiotherapy — is an option where surgery is not possible, and some small dogs do well. Arthritis progresses more in unstable joints.
Recovery
This is the part owners underestimate, and it determines the outcome as much as the surgery does.
Weeks 1–2: strict confinement. Lead-only toilet trips, no stairs, no jumping, no slippery floors. A crate or a small pen.
Weeks 2–8: gradually increasing lead walks, from a few minutes several times a day, building slowly.
Weeks 8–12: longer lead walks, beginning controlled exercises.
Months 3–6: gradual return to off-lead exercise, if the recheck confirms healing.
Throughout:
- Physiotherapy and hydrotherapy make a genuine difference. Ask for a referral — this is not an optional extra
- Non-slip flooring. Runners on hard floors, because a slip during recovery can undo the repair
- Ramps for the car
- Weight control. If your dog is overweight, this is the moment
- Mental enrichment, since a confined dog with nothing to do is miserable and hard to keep quiet
Some links on this page are affiliate links. If you buy through them we may earn a small commission at no extra cost to you — it helps keep this site free. We only recommend products we would use with our own dogs.
Snuffle Mat for Dogs
Crate rest is the hardest part of recovery for everyone. Scent games meet a dog’s needs while they are physically restricted, and they can be done lying down.
Bedsure Orthopedic Dog Bed
A firm supportive bed with a low entry matters during recovery and afterwards. A stiff post-operative dog struggling out of a soft collapsed bed is doing exactly the movement you are trying to protect.
Reducing the risk to the other leg
Since roughly half of dogs go on to rupture the second:
- Keep them lean. This is the biggest lever
- Build and maintain muscle through consistent moderate exercise
- Avoid the weekend-warrior pattern — a sedentary week then a hard hike
- Avoid repetitive high-speed turning, which means rationing hard ball chasing
- Non-slip flooring at home
- Discuss neutering timing with your vet for a young large-breed dog
Prognosis
Good. Most dogs return to full or near-full function after surgery and appropriate rehabilitation. Arthritis in that joint is essentially inevitable long-term, but it is manageable, and a lean dog with good muscle copes with it well.
The two things that most influence the outcome are the rehabilitation you do in the first three months and the dog’s body weight for the rest of their life. Both are yours.
