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Can a Dog Re-Tear ACL After TPLO Surgery?

Can a Dog Re-Tear ACL After TPLO Surgery?

TPLO

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Owners

Learn if a dog can re-tear the ACL after TPLO surgery, signs to watch for, and how to prevent re-injury effectively.

By 

Sustainable Vet Group

Updated on

August 13, 2026

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This article is for informational purposes only and is not a substitute for professional veterinary advice. Every case is unique, so always consult your veterinarian for guidance specific to your pet.

This content is intended for veterinary professionals for educational purposes. It does not replace clinical judgment or tailored advice. Always rely on your training, expertise, and the specific context of your patients.

Can a Dog Re-Tear ACL After TPLO Surgery?

TPLO surgery does not repair or replace the torn CCL it changes the biomechanics of the stifle so the CCL is no longer needed. This means there is no ligament to re-tear.

The question most owners are really asking is: can the operated knee fail again? The answer requires separating the different ways a TPLO can stop working well.

 

Quick answer: Dogs cannot re-tear the CCL after TPLO because TPLO makes the ligament unnecessary. Late meniscal tears occur in 5% of dogs. Contralateral rupture is the biggest risk: 22 to 54% rupture the other knee within 6 to 17 months.

 

Key takeaways

  • Dogs cannot re-tear the CCL after TPLO: TPLO changes joint geometry so the CCL is unnecessary; no ligament remains to re-tear
  • Late meniscal tears affect approximately 5% of dogs with intact meniscus at TPLO; they are the most common cause of sudden lameness regression
  • 30 to 40% of dogs have concurrent meniscal injury treated at TPLO surgery; this is not the same as a late post-operative tear
  • Contralateral CCL rupture is the biggest re-injury risk: 22 to 54% of dogs rupture the other knee within 6 to 17 months
  • Sudden non-weight-bearing after previous progress is the main warning sign for any post-TPLO complication it requires prompt veterinary evaluation
  • Implant failure is a hardware problem, not a CCL re-tear; it presents with sudden lameness and is diagnosed on radiographs

Why dogs cannot re-tear the CCL after TPLO

TPLO surgery works by rotating the tibial plateau to approximately 5 degrees. At this angle, the stifle is mechanically stable during weight-bearing without the cranial cruciate ligament.

The torn CCL is not repaired, reconstructed, or replaced.

Because no ligament substitute is in place, there is nothing to re-tear.

The joint stability provided by TPLO is structural it comes from the new bone geometry, not from any biological or synthetic material that could fail.

This is different from human ACL surgery, which typically involves a ligament graft (autograft or allograft) that can be re-torn.

Dog owners familiar with human ACL surgery often incorrectly assume the same risk applies after TPLO.

What can go wrong with the operated knee after TPLO

Late meniscal tears

This is the most important cause of sudden lameness regression after successful TPLO recovery.

TPLO Austin confirms: approximately 5% of dogs with an intact meniscus at the time of surgery will develop a meniscal tear at some point in the future.

When this occurs, patients may become acutely lame. In some cases, a second surgery is needed to remove the torn portion of the meniscus.

Laguna Hills Animal Hospital notes that dogs with a meniscal tear frequently exhibit a meniscal click an audible clicking noise as one of the telltale signs of injury.

Signs of a late meniscal tear:

  • Sudden regression to significant lameness after the dog was progressing well
  • Clicking or clunking sound from the knee during movement
  • Swelling of the stifle joint
  • Reluctance to bear full weight on a leg that was previously well-recovered

Vetplayas confirms that early identification and intervention for meniscal tears after TPLO are crucial to prevent further damage, chronic pain, and decreased joint function.

Tibial tuberosity fracture

This is a rare but serious complication occurring in 1 to 9% of TPLO cases (Laguna Hills Animal Hospital).

The tibial tuberosity the bony prominence where the patellar tendon inserts can fracture if placed under excessive stress, particularly in large, active dogs during the early healing phase.

Sudden severe lameness in the first weeks after surgery is the presentation. Radiographs confirm the diagnosis.

Implant failure (plate or screw problems)

If the TPLO plate bends, breaks, or screws loosen, the osteotomy site loses support and the bone may shift. This produces sudden or progressive lameness and is confirmed on radiographs.

Premature return to activity, obesity, and overexertion during the healing phase are the main risk factors for implant failure. For the full guide, see TPLO implant failure signs and causes.

The most important re-injury risk: the other knee

The operated knee rarely fails after successful TPLO recovery. The far greater risk is the other knee.

PMC (NCBi 2014) confirms that among dogs with unilateral CCL rupture, a large proportion will develop contralateral CCL rupture within 12 to 24 months.

The risk is 22 to 54% at 6 to 17 months of initial diagnosis.

This is because both CCLs are affected by the same systemic risk factors: genetics, body weight, conformation, and hormonal environment.

The degeneration that caused one CCL to fail is almost certainly affecting the other.

Weight management is the most impactful owner action for reducing the risk of contralateral rupture. Maintaining a lean body condition score reduces mechanical load on both stifle joints simultaneously.

Signs that the operated knee has a new problem

Contact your veterinarian if you notice:

  • Sudden regression to non-weight-bearing or severe lameness after the dog was progressing well
  • A new clicking or popping sound from the operated knee
  • New swelling or heat at the operated knee months after surgery
  • Progressive rather than improving lameness between weeks 8 and 16

Contact your veterinarian about the other knee if you notice:

  • New hind limb lameness on the opposite side
  • Bilateral stiffness, especially in the morning
  • Sitting with one leg extended to the side (the opposite leg from the TPLO)

For the TPLO failure rate context, see TPLO failure rate in dogs explained. For the meniscal complication guide, see dog meniscus tear after TPLO: symptoms and solutions.

For the full complications reference, see 15 common complications after TPLO surgery in dogs. For signs of lameness and their causes, see lameness after TPLO surgery in dogs.

For guidance on return-to-activity, see when can dogs resume agility training post-TPLO?.

Frequently asked questions

My dog had TPLO and is suddenly limping badly again. Did they re-tear their ACL?

Not in the literal sense TPLO does not leave a CCL to re-tear.

Sudden regression after successful initial recovery is most likely a late meniscal tear, though implant complications, infection, or patellar issues can also present this way.

Any sudden regression to severe lameness after TPLO warrants same-day or next-day veterinary evaluation.

How can I tell if it's a meniscal tear vs. a plate problem?

A meniscal click or clunk during movement is more characteristic of meniscal injury. Implant failure is more likely to show subtle progressive changes visible on radiographs.

A vet cannot reliably distinguish them on clinical examination alone radiographs and often arthroscopy are needed.

Can TPLO surgery fail entirely?

Complete failure where the joint reverts to pre-surgical instability is uncommon. Partial complications (late meniscal tear, infection, implant issues) are more typical. The overall reoperation rate for TPLO complications is below 10%.

Most dogs that have successful initial recovery maintain good long-term function.

How do I reduce my dog's risk of a late meniscal tear after TPLO?

Strict activity restriction for the full 8 to 12 weeks minimizes abnormal forces on the healing meniscus. Maintaining healthy body weight reduces meniscal loading throughout the dog's life.

The surgeon assesses the meniscus at TPLO if it was already damaged and removed, a late tear in that knee is no longer possible.

Should I worry about my dog's other knee after TPLO?

Yes the contralateral CCL rupture risk of 22 to 54% within 6 to 17 months is substantial.

Weight management, consistent controlled exercise, and watching for new lameness on the opposite side are the appropriate responses.

Early diagnosis and surgery on the second knee (when it ruptures) produce the same good outcomes as the first.

Resources

  • TPLO Austin. Step 6: TPLO Surgery Recovery. tploaustin.com
  • Laguna Hills Animal Hospital. TPLO Surgery Complications. lhah.com
  • Vetplayas. Dog Meniscus Tear After TPLO: Understanding and Managing the Complication. vetplayas.com
  • PMC. Radiographic Risk Factors for Contralateral Rupture in Dogs with Unilateral CCL Rupture. ncbi.nlm.nih.gov
  • ACVS. Cranial Cruciate Ligament Disease. acvs.org

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