Torn ACL in Dogs: Symptoms, Surgery, Cost and Recovery

What Is a Torn ACL in Dogs?

Dogs have two cruciate ligaments inside each knee (stifle). The cranial cruciate ligament, the equivalent of a person's ACL, stops the shin bone sliding forward under the thigh bone.⁵ In most dogs, the ligament degenerates slowly over time. Partial tears almost always progress to a full tear over time.¹ Once it tears, the knee becomes unstable, which causes pain, damages the meniscus (the knee's cartilage cushion) and leads to arthritis.^3,1 Between 20% and 77% of dogs with a ruptured cruciate also have meniscal damage, depending on the study.^3,10 For an overview of other knee conditions, see dog knee problems.

Symptoms of a Torn ACL

• Sudden lameness on a back leg, or only touching the toes down, with a complete tear⁵
• A limp that comes and goes, often worse after exercise or rest, with a partial tear^5,1
• Sitting with the affected leg kicked out to the side (a "lazy sit")⁵
• Trouble getting up, jumping or climbing stairs⁵
• Swelling of the knee, or a firm thickening on the inner side over time³
• A clicking sound when walking, which can mean the meniscus is torn too
• Thigh muscle loss on the affected leg⁵

Which Dogs Get Torn ACLs?

• Breeds: Rottweilers have the highest risk in UK studies. West Highland White Terriers, Golden Retrievers, Bichon Frises, Yorkshire Terriers and Staffordshire Bull Terriers are also over-represented; Labradors and Newfoundlands are commonly affected too.^6,11,3
• Weight: Heavier dogs, including overweight dogs, have higher risk.^6,5
• Age: Most dogs are middle-aged or older; in one large UK study the average age at diagnosis was 7.4 years.¹¹
• Neutering: Neutered dogs have higher odds of cruciate disease in several studies. In one university-hospital study of Golden Retrievers neutered before a year old, 5% of males and 8% of females tore a cruciate ligament, compared with none of the intact dogs.^6,12,13 The best timing for neutering depends on breed and other factors, so discuss it with your vet.
• Other knee problems: Dogs with a slipping kneecap are more likely to tear a cruciate ligament.^14,15

How Vets Diagnose a Torn ACL

Your vet will check for abnormal movement in the knee using the "drawer" test and the tibial thrust test. Light sedation is sometimes needed, especially for tense dogs or partial tears, which can be harder to detect.^1,5,3 The ligament itself doesn't show on X-rays, but X-rays show joint swelling and arthritis and are needed to plan surgery.^5,1

ACL Surgery Options for Dogs

Surgery stabilizes the knee and lets the surgeon check and treat the meniscus. Significant improvement is reported in 85% to 90% of dogs.¹

• TPLO (tibial plateau leveling osteotomy). The top of the shin bone is cut, rotated and held with a plate so the knee no longer relies on the torn ligament. It's the procedure with the strongest evidence for returning dogs to normal function, especially larger and active dogs.^16,17,18
• TTA (tibial tuberosity advancement). The front of the shin bone is moved forward to change the forces on the knee. Results and complication rates are broadly similar to TPLO in most studies.⁹
• Lateral (extracapsular) suture. A strong suture outside the joint mimics the ligament while scar tissue forms. It's usually less expensive and is often used for smaller dogs. The most common problems are suture failure and arthritis.^1,2

Complications such as infection, implant problems or a later meniscal tear occur in a minority of dogs. Reported overall complication rates are mostly around 10% to 20%, with some studies reporting more, and major complications, some needing another operation, occur in roughly 5% to 11%.^10,19,9 A later meniscal tear occurs in about 2% to 30% of dogs, depending on the technique.³

How Much Does Dog ACL Surgery Cost?

Costs vary widely by region, clinic and your dog's size, and usually cover one knee:

• A US university hospital quoted $4,000 to $4,500 for TPLO in small to large dogs, and $4,500 to $5,000 for giant breeds (2021).¹⁹
• Pet insurer claims data put the average cruciate repair at about $3,800, and costs can exceed $5,000 per knee (2017).²⁰
• A pet insurer's 2026 guide estimates TPLO at $6,000 to $10,000 per leg.²¹

Lateral suture repair is usually less expensive than TPLO or TTA. Ask for a written estimate that includes X-rays, pain medicine and recheck visits. If cost is a concern, ask your vet about payment plans, a veterinary school, or which option fits your dog's size.

Recovery After ACL Surgery

• First 8 weeks: strict rest with short leash walks only; no running, jumping, playing or stairs. Follow-up X-rays are usually taken at about 8 weeks.¹⁹
• Weeks 8 to 16: a gradual increase in leash walking. Most dogs return to normal activity at 3 to 4 months.²
• Full recovery: many dogs reach full function by about a year.¹⁹
• Physical rehabilitation, weight control and a cone to protect the incision all help recovery.

Can a Dog Recover From a Torn ACL Without Surgery?

Some can, particularly small dogs. In an older study, 86% of dogs under 15 kg (33 lb) were normal or improved with conservative care, compared with only 19% of heavier dogs.²² In a randomized trial of overweight dogs, 64% managed without surgery had a successful outcome at one year, compared with 75% after TPLO, and surgically treated dogs did much better at 6 months; only 11 of the 20 non-surgical dogs remained in the study at one year.²³ Conservative care means several weeks of strict rest, weight loss, vet-prescribed pain relief and physical rehabilitation.^22,5 It doesn't restore a fully stable knee, so arthritis progresses faster than after surgery.¹

Knee braces: Custom braces are an option for dogs that can't have surgery, but the evidence is limited. In one owner survey, 86% of brace owners rated the outcome good or better, compared with 98% after TPLO, and 46% of brace users had skin problems.^24,1,25

Can You Prevent It?

Keeping your dog at a healthy weight is the most practical step, since heavier dogs have higher risk.⁶ Regular moderate exercise to keep muscles strong, rather than occasional bursts of intense activity, is commonly recommended. If your dog has already torn one ligament, ask your vet how to protect the other knee, since many dogs tear both.^7,1

See arthritis in dogs and why dogs limp.

Frequently Asked Questions

Is ACL surgery worth it for a dog?

For most medium and large dogs, yes. Surgery gives the most stable knee and reduces long-term lameness. Some small dogs do well without it.

Is it painful for a dog to live with a torn ACL?

Yes, especially at first. Pain often eases over weeks, but the unstable knee continues to develop arthritis and can damage the meniscus.

Can a dog's torn ACL heal on its own?

No. The ligament doesn't grow back together, but scar tissue can stabilize the knee somewhat, mainly in small dogs.

How much does a dog's ACL surgery cost?

US estimates range from about $3,800 to $5,000 per knee in older data to $6,000 to $10,000 in a 2026 insurer guide.

What's the difference between TPLO and lateral suture?

TPLO changes the angle of the shin bone with a cut and a plate. Lateral suture uses a strong suture outside the joint. TPLO has better evidence for large, active dogs.

How long is recovery from ACL surgery?

About 8 weeks of strict rest, then a gradual return to activity. Most dogs are back to normal at 3 to 4 months.

Will my dog tear the other ACL?

Many do. Studies report that roughly 30% to 60% of dogs later tear the other cruciate ligament.

Should I put my dog down if I can't afford ACL surgery?

Usually not. Many dogs, especially small ones, can have a good quality of life with conservative care, pain relief and rehab. Ask your vet about lower-cost options.