The Modified Maquet Procedure (MMP) is an evolution of the Tibial Tuberosity Advancement (TTA) that uses a titanium foam wedge instead of a cage to advance the tibial tuberosity.

It has been positioned as a less invasive, faster-to-perform alternative to TPLO for dogs with CCL rupture.

Published clinical evidence shows both procedures produce good outcomes, with TPLO demonstrating a slight advantage in objective gait analysis at 3 months.

Quick answer: A prospective randomized study found TPLO achieves 93.9% of normal peak vertical force vs 89.4% for MMP at 6 months — no significant difference in complications or OA progression. MMP is less invasive, faster, and generally less expensive. Both are appropriate for medium-to-large breed dogs.

Key takeaways

• TPLO achieves 93.9% of normal ground reaction force at 6 months vs 89.4% for MMP — numerically superior but not statistically significant
• No significant difference in major complications or OA progression was found between TPLO and MMP in the comparative study
• MMP is less invasive and faster to perform: a titanium foam wedge and partial osteotomy instead of TPLO's full proximal tibial cut
• MMP is generally less expensive than TPLO: shorter surgical time and different implant costs reduce the procedure price
• Early partial weight-bearing may occur sooner after MMP due to less invasive fixation and the partial osteotomy
• TPLO has a much larger evidence base: 25+ years of data vs limited MMP evidence

How each procedure works

TPLO (Tibial Plateau Leveling Osteotomy)

TPLO addresses CCL rupture by making a curved osteotomy through the proximal tibia and rotating the tibial plateau to approximately 5 degrees.

This changes joint biomechanics so the stifle is stable during weight-bearing without a functioning CCL. The osteotomy is held in place with a bone plate and screws.

Modified Maquet Procedure (MMP)

MMP is an adaptation of TTA in which the tibial tuberosity is advanced cranially by making a partial osteotomy in the tibial crest.

A porous titanium foam wedge is inserted into the gap and a fixation staple holds the construct in position.

The cranial advancement of the tuberosity repositions the patellar tendon to neutralize the cranial thrust that occurs in the CCL-deficient stifle the same biomechanical principle as TTA, with different implants.

Animal Works Veterinary Surgery describes MMP as using improved implants and surgical techniques designed to reduce operating time and minimize complications compared to standard TTA.

The titanium foam wedge promotes bone ingrowth and healing without the need for a cage or plate system. Bone healing in the MMP osteotomy site is typically complete at 90 days radiographically.

Clinical evidence: TPLO vs MMP

Primary comparative study

PubMed (prospective randomized controlled study, 61 dogs, 76 joints): dogs were treated with TPLO (n=30, 41 joints) or MMP (n=31, 35 joints) and compared with healthy controls.

Outcomes were assessed by clinical examination, radiography, and treadmill force plate gait analysis at 6 weeks, 3 months, and 6 months.

Results at 6 months:

• TPLO: 93.9% of normal peak vertical force (PVF), 85.9% of normal vertical impulse (VI)
• MMP: 89.4% of normal PVF, 79.9% of normal VI

At 3 months, significantly more TPLO patients were within the reference range for healthy dogs on peak vertical force. By 6 months, the difference was not statistically significant.

No significant difference was found in major complications or OA progression at any time point.

Conclusion from the study: "Although no significant differences were found between the surgical methods, TPLO patients showed superiority with regard to clinical outcome."

MMP standalone study

PMC (35 dogs, unilateral CCL rupture, MMP): significant improvement in ground reaction forces at all time intervals. At 90 days, 54.2% of patients had a Symmetry Index suggesting normal gait.

Complete bone healing on radiographs at 90 days. Major complication rate: 8.5% (3 of 35), minor complication rate: 2.8%.

Practical comparison

Which dogs are best suited to each?

MMP is often chosen for:

• Medium and large breed dogs where a less invasive approach is preferred
• Cases where surgical time is a clinical consideration
• Practices experienced in MMP technique
• Dogs where cost is a factor

TPLO is typically recommended for:

• Large and giant breed dogs with high joint loads
• Dogs with steep tibial plateau angles where TPLO provides more precise biomechanical correction
• Cases where the largest available evidence base is preferred
• Surgeons with established TPLO experience

Animal Hospital of Adel notes that both surgeries are effective, with MMP being less invasive, less expensive, and quicker to perform.

Walkerville Vet's evidence review concludes that TPLO gives slightly better objective results and that MMP is expected to outperform standard TTA, though more evidence is needed.

For the full TPLO pros and cons, see TPLO surgery pros and cons for dogs. For the full alternatives overview, see alternatives to TPLO surgery for dogs.

Frequently asked questions

Is MMP as effective as TPLO for large dogs?

The evidence suggests TPLO has a slight advantage at 3 months, with equivalent outcomes by 6 months in the primary comparative study.

Most surgeons still prefer TPLO for large and giant breeds due to the larger evidence base and slightly superior short-term objective results. MMP is appropriate for many large dogs in experienced hands.

How much cheaper is MMP than TPLO?

MMP is generally less expensive than TPLO due to shorter surgical time and different implant costs. The specific difference varies by practice, region, and surgeon.

Ask your veterinarian for a direct cost comparison for your dog's specific case.

What is the complication rate for MMP compared to TPLO?

The MMP standalone study reported an 8.5% major complication rate. TPLO complication rates across the literature range from 14 to 34%.

However, these figures come from different study populations and settings, making direct comparison difficult. Neither procedure is free of risk.

How long does MMP recovery take compared to TPLO?

Both procedures require 8 to 12 weeks of restricted activity, though MMP's less invasive partial osteotomy may allow earlier partial weight-bearing in some dogs.

Full activity return for both procedures is typically at 4 to 6 months.

Can a dog have TPLO if MMP fails?

Yes. TPLO can be performed as a revision if MMP results in ongoing instability or poor function. The converse is less common.

Discuss revision options with an orthopedic specialist if your dog is not progressing as expected after MMP.

Resources

• PubMed. Outcome after Tibial Plateau Levelling Osteotomy and Modified Maquet Procedure in Dogs with CCL Rupture. pubmed.ncbi.nlm.nih.gov
• PMC. Outcome after Modified Maquet Procedure in Dogs: Force Plate Gait Analysis. ncbi.nlm.nih.gov
• Animal Works Veterinary Surgery. MMP vs TPLO. animalworksvets.com
• Dog Knee Injury. Modified Maquet Procedure (MMP Surgery) for Dogs. dogkneeinjury.com
• Walkerville Vet. Which ACL Surgery Is Best for Dogs? walkervillevet.com.au

Patellar tendonitis more precisely called patellar desmopathy or patellar ligament desmitis in veterinary literature is a recognized complication of TPLO surgery. It is also one of the most under-discussed.

Research published in PMC shows radiographic evidence of patellar ligament thickening in 93% of dogs at 4 weeks after TPLO, though most cases are asymptomatic.

Understanding what this condition is, when it becomes a clinical problem, and how it is treated helps owners navigate one of the more commonly missed post-TPLO findings.

Quick answer: Patellar desmitis after TPLO is inflammation and thickening of the patellar ligament. Radiographic thickening occurs in 93% of TPLO dogs at 4 weeks but is usually asymptomatic. Clinically significant cases cause pain and increased lameness. Most are self-limiting; shock wave therapy accelerates resolution.

Key takeaways

• Radiographic patellar ligament thickening occurs in 93% of TPLO dogs at 4 weeks: most are asymptomatic and self-limiting
• Clinically significant patellar desmitis causes pain, swelling, and increased lameness beyond expected post-op discomfort
• TPLO changes stifle biomechanics and increases patellar tendon load: this explains why desmitis occurs more after TPLO
• Shock wave therapy (SWT) significantly reduced patellar ligament thickness at weeks 6 and 8 in a 2012 clinical trial
• Most cases are self-limiting: rest and NSAIDs resolve the majority of clinically significant cases within weeks to months
• Excessive post-operative activity is a modifiable risk factor: strict restriction in the first 8 weeks reduces desmitis risk

What is patellar desmitis after TPLO?

The patellar ligament runs from the kneecap (patella) to the tibial tuberosity — the bony bump just below the knee on the front of the tibia.

It is a critical structure for leg extension and stifle stability.

After TPLO surgery, the biomechanics of the stifle change fundamentally. The tibial plateau is rotated and held at a new angle.

This changes how forces are distributed around the knee, including the forces that pass through the patellar ligament.

The patellar ligament experiences altered tension and loading patterns after TPLO that it did not experience before surgery.

PMC research (2025 retrospective study) confirms desmopathy typically develops within 2.5 months after surgery, affecting the distal portion, and that TPLO causes more ligament thickening than other CCL repair methods.

A separate PMC study using elastosonography confirmed that patellar tendon tendinopathy can be easily detected clinically but that the exact damage evaluation is challenging without ultrasound or advanced imaging.

Why does TPLO cause patellar tendonitis?

Several mechanisms contribute:

Altered stifle biomechanics: TPLO changes the angle of the tibial plateau and the position of the tibial tuberosity relative to the femur. This alters patellar tendon geometry and tension during weight-bearing.

Surgical trauma: retraction and manipulation of soft tissues around the tibial tuberosity during the procedure causes local inflammatory changes that can involve the patellar tendon.

Intraoperative tension increase: rotating the proximal tibial segment may change the tension in the patellar tendon directly, especially during the initial healing phase.

Excessive postoperative exercise: Clinicians Brief's treatment review notes that excessive postoperative exercise is a commonly proposed contributing factor. Dogs allowed too much activity too early are more likely to develop clinically significant desmitis.

How common is patellar desmitis after TPLO?

Radiographic evidence of patellar ligament thickening at 4 weeks post-TPLO is reported in 93% of dogs in clinical studies.

The vast majority of these dogs have no clinical signs the radiographic finding does not translate into a symptomatic problem for most patients.

Clinically significant desmitis where the dog shows pain and lameness attributable to the patellar ligament specifically is less common but well-recognized by veterinary orthopedic surgeons.

Laguna Hills Animal Hospital notes that patellar tendinosis is relatively benign in most cases and improves with rest and medication.

Signs of clinically significant patellar desmitis

Unlike the asymptomatic radiographic finding, clinical patellar desmitis produces:

• Pain on direct palpation of the patellar ligament (between the kneecap and tibial tuberosity)
• Swelling or thickening directly over the ligament
• Lameness that is worse than expected for the dog's recovery stage
• Reluctance to fully extend the stifle during walking or exercise
• Stiffness after rest that improves briefly with movement

These signs typically appear in the first 6 to 10 weeks after TPLO.

Diagnosis

A veterinarian diagnoses patellar desmitis through:

Physical examination: palpation of the patellar ligament for thickening, pain response, and heat. A dog with significant desmitis will react to direct pressure on the ligament.

Radiographs: thickening of the soft tissue shadow over the patellar ligament on a lateral stifle projection. This is often identified at the routine 4 to 6 week post-TPLO radiographic recheck.

Ultrasound: provides direct visualization of the ligament, showing thickening, fiber disruption, and periligamentous edema. Ultrasound is more sensitive than radiographs and is the preferred modality for detailed assessment.

Treatment

Rest and activity restriction

The foundation of treatment for most cases. Reducing the mechanical load on the patellar ligament allows the inflammatory process to resolve.

Strict activity restriction should already be in place for post-TPLO recovery patellar desmitis is a reason to enforce it rigorously.

NSAIDs

Anti-inflammatory medication reduces pain and local inflammation. Meloxicam or carprofen at appropriate veterinary doses is the standard pharmaceutical approach for most dogs with symptomatic desmitis.

Shock wave therapy (SWT)

Clinicians Brief reviewed a trial of 30 large-breed TPLO dogs: SWT at weeks 4 and 6 significantly reduced patellar ligament thickness on radiographs at weeks 6 and 8 vs. controls.

SWT should be considered for dogs with clinically significant patellar desmitis.

Laser therapy

Low-level laser therapy (photobiomodulation) may reduce local inflammation and support tissue healing, though evidence specific to patellar desmitis after TPLO is limited compared to the SWT evidence base.

For the complete TPLO complications reference, see 15 common complications after TPLO surgery in dogs. For the incision infection guide, see TPLO incision infection symptoms and prevention.

For the general lameness guide that helps distinguish desmitis from other causes of post-TPLO lameness, see lameness after TPLO surgery in dogs.

For the TPLO failure rate context, see TPLO failure rate in dogs explained.

Frequently asked questions

Is patellar tendonitis after TPLO serious?

In most dogs, no. The radiographic finding is near-universal but typically asymptomatic and self-limiting.

Clinically significant desmitis causes pain and increased lameness but usually resolves with rest, NSAIDs, and sometimes shock wave therapy. It rarely causes permanent dysfunction.

How do I know if my dog has patellar tendonitis vs. normal post-TPLO soreness?

The key distinguishing feature is pain specifically on palpation of the patellar ligament the structure running from the kneecap to the bump just below the knee.

Normal post-TPLO soreness is diffuse and improves steadily. Patellar desmitis produces focal pain at this location, often with visible swelling over the ligament.

Can patellar desmitis be prevented?

Strict activity restriction in the first 8 weeks post-TPLO is the most effective preventive measure, since excessive early activity is a recognized contributing factor.

It cannot always be prevented altered biomechanics from the surgery itself play a role regardless of activity level but minimizing mechanical load during the healing phase reduces severity.

Does patellar tendonitis require a second surgery?

Almost never. The vast majority of cases resolve with conservative management. Shock wave therapy is effective in cases that need more active treatment.

Surgical intervention for patellar desmitis after TPLO is extremely rare.

Will this affect my dog's long-term outcome after TPLO?

For most dogs, no. Clinically significant patellar desmitis is typically a temporary complication that resolves during the recovery period.

Long-term stifle function in dogs that develop and recover from patellar desmitis is generally comparable to dogs that do not develop the condition.

Resources

• PMC. Retrospective Study on Patellar Desmopathy Following Surgical Resolution of CCL Rupture in 28 Dogs. ncbi.nlm.nih.gov
• PMC. Radiographic, Ultrasonographic and Shear Elastosonographic Changes in Patellar Ligament in Dogs Undergoing TPLO. ncbi.nlm.nih.gov
• Clinicians Brief. Treating Patellar Ligament Desmitis. cliniciansbrief.com
• Laguna Hills Animal Hospital. TPLO Surgery Complications. lhah.com
• ACVS. Cranial Cruciate Ligament Disease. acvs.org

TPLO plate rejection is one of the less common but more serious complications that can follow tibial plateau leveling osteotomy surgery.

The term "rejection" is sometimes used loosely distinguishing between true immune-mediated rejection, infection, and implant loosening matters because the treatment differs significantly for each.

Quick answer: True TPLO plate rejection is rare — implants are highly biocompatible. It produces persistent swelling, heat, pain over the plate, and sometimes a draining tract. Infection produces identical symptoms. Contact your vet if lameness worsens or discharge appears weeks to months after surgery.

Key takeaways

• True immune-mediated plate rejection is rare: TPLO plates are made from highly biocompatible titanium or stainless steel
• Symptoms overlap significantly with infection: pain, swelling, heat, and discharge occur in both; bacterial culture distinguishes them
• Infection is the most common implant complication: TPLO infection rates range from 0.8 to 14.3%; true rejection is a small subset
• Signs typically appear weeks to months after surgery: worsening lameness after initial improvement is the classic red flag
• A draining tract (fistula) over the plate is a hallmark sign of implant-associated infection or rejection
• True rejection requires plate removal: once the osteotomy heals (at least 12 weeks), the plate is removed; bone heals without it

What is TPLO plate rejection?

The TPLO plate and screws are made from medical-grade titanium or stainless steel.

These materials are designed to be biologically inert the body should recognize them as neutral foreign material and wall them off without reaction.

Laguna Hills Animal Hospital explains that in some cases, the TPLO plate is rejected by the dog's body because it is perceived as a foreign object.

True immune-mediated rejection occurs when the immune system mounts an inflammatory response against the implant material itself. This is distinct from:

• Periprosthetic infection: bacteria colonize the implant surface and cause chronic infection around the plate; this is far more common than true rejection
• Mechanical failure: the plate bends, breaks, or screws loosen due to excessive force; this is a structural problem, not an immune reaction
• Normal post-surgical inflammation: expected in the first 2 to 3 weeks; should be improving, not worsening

In clinical practice, the distinction between true rejection and low-grade infection is often made by bacterial culture of the fluid or tissue at the site.

True aseptic rejection produces inflammation without bacterial growth; periprosthetic infection produces the same symptoms with positive cultures.

Symptoms of TPLO plate rejection

Dog Discoveries' veterinary reference describes plate rejection as: the knee becomes inflamed and sore around the plate, the dog feels constant pain and irritation, and the dog gets worse rather than better.

Signs of trouble are generally seen weeks to months after surgery rather than in the immediate post-operative period.

Key symptoms to monitor:

Worsening or persistent lameness: a dog that was improving and then regresses, or one whose lameness fails to improve beyond the expected baseline, is showing a key red flag. This is distinct from the expected early post-TPLO lameness that should be progressively improving week by week.

Localized swelling over the plate: visible or palpable swelling directly over the plate site (proximal medial tibia) that does not resolve with rest and is not reducing over time.

Warmth and heat at the surgical site: warmth beyond the first 2 to 3 post-operative weeks suggests ongoing inflammation.

Draining tract (fistula): a small hole in the skin near the surgical site that produces persistent clear, bloody, or purulent discharge. This is a hallmark of implant-associated complications either infection or reaction. Vet Playas confirms persistent drainage or discharge, especially with a foul odor, may indicate infection or plate rejection.

Pain on palpation: the dog reacts to direct pressure over the plate site.

Failure to heal: the dog is not progressing as expected at radiographic rechecks; osteotomy bridging is delayed or absent.

How plate rejection is diagnosed

Clinical examination: systematic palpation of the plate site, assessment of lameness grade, and comparison to expected recovery trajectory.

Radiographs: assess osteotomy healing, implant position, screw integrity, and periimplant bone quality. Periprosthetic bone loss suggests infection or chronic reaction.

Culture and sensitivity: fluid or tissue from the surgical site is cultured to determine whether bacteria are present and which antibiotics are effective. Culture-negative inflammation supports true rejection; culture-positive results confirm infection.

Blood work: elevated inflammatory markers (C-reactive protein, white blood cell count) confirm systemic involvement.

Treatment

For infection (most common implant complication)

Culture-directed antibiotic therapy is initiated. If the osteotomy is not yet healed, the plate must remain in place removing the plate before the osteotomy heals causes the bone segments to lose support.

Targeted antibiotics and local wound management may control infection until healing is sufficient.

If the infection does not resolve with antibiotics, surgical debridement or implant removal (if the bone has healed) may be required.

For the full infection management guide, see TPLO plate infection signs and treatment.

For true aseptic rejection

Plate removal is the definitive treatment. Laguna Hills Animal Hospital confirms that the bone plate must remain in place for at least 12 weeks to allow the bone to heal.

Once healing is confirmed radiographically typically at 10 to 12 weeks the plate can be safely removed.

The bone does not require the plate long-term; it is a scaffold to hold the osteotomy while it heals.

When to contact your veterinarian

Contact your vet if:

• Lameness worsens or plateaus instead of progressively improving
• You notice new swelling, heat, or discharge at the surgical site weeks after surgery
• A draining tract appears at or near the incision
• Your dog shows signs of pain at the plate site on palpation
• Radiographs at rechecks show unexpected findings around the plate or screws

For the implant failure guide, see TPLO implant failure signs and causes. For the plate removal recovery guide, see TPLO plate removal recovery guide.

For the full complications reference, see 15 common complications after TPLO surgery in dogs. For the plate infection article with antibiotic treatment details, see TPLO plate infection signs and treatment.

For when the plate needs to come out due to infection, see when does a TPLO implant need to be removed due to infection.

Frequently asked questions

How common is TPLO plate rejection in dogs?

True immune-mediated rejection is uncommon. TPLO plates are manufactured from highly biocompatible titanium or stainless steel.

The more common implant complication is infection (0.8 to 14.3% of TPLO cases depending on the study), which produces similar symptoms to rejection.

Metal allergy or true rejection accounts for a small subset of these cases.

How do I know if it's plate rejection or infection?

The symptoms overlap significantly. Bacterial culture of fluid from the site distinguishes them: culture-positive means infection; culture-negative inflammation in the right clinical context suggests true rejection.

Both require veterinary evaluation do not attempt to manage either at home.

Can the plate stay in if my dog is rejecting it?

No. If true rejection is diagnosed and the plate is causing ongoing inflammation, it must be removed once the osteotomy has healed sufficiently.

Most dogs do not require the plate after 10 to 12 weeks once the bone has consolidated. Plate removal is a less complex procedure than the original TPLO.

Will my dog need another surgery if the plate is rejected?

Plate removal surgery is typically required if true rejection is confirmed and the osteotomy has healed. This is less invasive than the original TPLO.

In most cases the dog recovers well after plate removal, and long-term outcomes are good.

Can rejection be prevented?

Pre-surgical screening for metal sensitivities can help select the best implant material. Strict aseptic technique during surgery minimizes infection that can mimic rejection.

Activity restriction during recovery reduces mechanical stress on the implant that increases complication risk.

Resources

• Dog Discoveries. Signs of TPLO Plate Rejection in Dogs. dogdiscoveries.com
• Vetplayas. Unveiling TPLO Plate Rejection Symptoms. vetplayas.com
• Laguna Hills Animal Hospital. TPLO Surgery Complications. lhah.com
• ACVS. Cranial Cruciate Ligament Disease. acvs.org

Urinary incontinence after TPLO surgery is not a common complication, but it does occur and is understandably alarming for owners.

In most cases it is a temporary consequence of anesthesia, pain medication, stress, or reduced mobility not a sign of a serious surgical problem.

Knowing the causes, the timeline, and when to call your vet helps you respond appropriately.

Quick answer: Incontinence after TPLO is usually temporary from anesthesia, pain medications, reduced mobility, or stress. Most cases resolve within days to weeks. Call your vet if it persists beyond 2 to 4 weeks or comes with bloody urine or fever.

Key takeaways

• Immediate post-TPLO incontinence is most often from anesthesia or nerve irritation: both are temporary and resolve within days to weeks
• Opioid pain medications cause urinary retention or reduced bladder awareness in some dogs this resolves as medications are tapered
• Postoperative swelling may temporarily irritate nerves involved in bladder control; this resolves with swelling
• Reduced mobility is a practical contributor: a confined, painful dog may not signal in time or reach the door quickly
• Stress after major surgery can cause accidents in previously house-trained dogs; this is behavioral, not neurological
• Genuine nerve damage from TPLO is rare: incontinence persisting beyond 6 weeks warrants neurological evaluation

Why dogs may become incontinent after TPLO surgery

Anesthesia effects

General anesthesia temporarily suppresses normal nerve function throughout the body, including the neural pathways that control bladder filling awareness and sphincter tone.

As anesthetic drugs are metabolized over the 12 to 24 hours after surgery, some dogs have reduced bladder control.

This is the most common cause of immediate post-surgical incontinence. It resolves as anesthesia fully clears, typically within 24 to 48 hours.

Nausea, disorientation, and general sedation from anesthesia also mean the dog may not signal clearly when they need to go outside.

Scheduled outdoor bathroom trips every 2 to 4 hours in the first 24 to 48 hours post-surgery help manage this.

Opioid and sedative medications

Opioid pain medications commonly prescribed after TPLO affect bladder control in two ways: they reduce awareness of bladder fullness, and in some dogs cause urinary retention.

Both effects resolve as medications are tapered in the days following surgery.

Retention and incontinence are opposite problems retention is not urinating at all, while incontinence is involuntary urination but both can occur at different times as different medications have their effects.

As pain medications are tapered in the days after surgery, these effects resolve for most dogs.

Postoperative swelling and nerve irritation

The proximal tibia is surrounded by neurovascular structures. Postoperative swelling around the surgical site may temporarily compress or irritate nerves that travel to the bladder and urethra.

This is more likely in the first week after surgery when swelling is at its peak.

This type of incontinence improves as swelling resolves and typically does not indicate permanent nerve damage.

Reduced mobility

A dog recovering from TPLO is confined, in pain, and may not reach the door quickly enough when the bladder signals urgency.

This is a practical mobility problem, not a neurological one.

Frequent scheduled outdoor trips every 2 to 4 hours in the first week reduce accidents significantly. Waterproof mattress covers and washable bedding help manage the recovery period hygienically.

Stress and behavioral response

Major surgery is a significant stressor. Pain, an unfamiliar environment, an E-collar, restricted movement, and disrupted routine can cause previously house-trained dogs to have accidents unrelated to neurological dysfunction.

This type of incontinence typically resolves as the dog settles into a recovery routine at home, usually within 1 to 2 weeks.

Pre-existing urinary conditions

Dogs with pre-existing urinary sphincter mechanism incompetence (common in middle-aged spayed females), bladder infections, or weak bladder control may show worsened incontinence after surgery.

Anesthesia, medications, and reduced mobility all unmask or worsen underlying conditions.

If your dog was occasionally leaking urine before surgery, report this to your vet during the pre-surgical assessment so appropriate management can be planned for the recovery period.

Types of post-TPLO incontinence by timing

Immediate (within 24 to 48 hours): almost always anesthesia effects or opioid medication. Expected and self-limiting.

Early post-operative (days 3 to 14): medication effects, swelling-related nerve irritation, mobility limitation, or stress. Usually self-limiting with appropriate management.

Delayed onset (weeks 2 to 6): may indicate a developing urinary tract infection (UTI), which can occur after catheterization during surgery or from reduced immune response. A urinalysis is warranted if incontinence appears or worsens after initial improvement.

Chronic (beyond 6 weeks): uncommon. If incontinence persists beyond 6 weeks without improvement, veterinary evaluation for nerve damage or underlying urinary tract disease is appropriate.

Home management during recovery

• Scheduled outdoor bathroom trips every 2 to 4 hours for the first 1 to 2 weeks
• Waterproof mattress protectors and washable bedding in the recovery area
• Non-slip surfaces to reduce the effort required to stand and move toward the door
• Monitor urine color and odor cloudy, bloody, or foul-smelling urine suggests UTI
• Keep the genital area clean to prevent skin irritation from urine contact
• Use a belly band (for males) or absorbent dog diapers if incontinence is significant

When to contact your veterinarian

Call your vet if:

• The dog cannot urinate at all for more than 12 to 24 hours after surgery
• Urine is bloody, cloudy, or has a strong unusual odor (UTI signs)
• Incontinence is accompanied by straining, crying during urination, or frequent squatting without producing urine
• Incontinence worsens after initial improvement
• The dog has persistent incontinence beyond 2 to 4 weeks without any improvement
• Incontinence is combined with significant worsening lameness or systemic signs

For the not-peeing guide that covers urinary retention after TPLO, see dog not peeing after TPLO surgery: causes and care.

For the full TPLO complications reference, see 15 common complications after TPLO surgery in dogs.

For TPLO plate infection signs that may be contributing to systemic effects, see TPLO plate infection signs and treatment.

For post-op whining that may relate to the same pain driving accidents, see dog whining after TPLO surgery: causes and care.

Frequently asked questions

Is incontinence normal after TPLO surgery?

Temporary incontinence particularly in the first 24 to 48 hours is a recognized post-surgical finding related to anesthesia and opioid pain medications.

It is not an expected routine outcome, but it is not rare. If it resolves within a few days, it was almost certainly anesthesia-related.

Could my dog have nerve damage from TPLO surgery?

True nerve damage causing persistent incontinence from TPLO is rare. TPLO is performed at the proximal tibia, which is some distance from the pelvic nerves controlling bladder function.

Temporary nerve irritation from swelling is much more common than actual nerve injury and resolves as swelling subsides.

My dog was continent before TPLO and is now leaking at night. Why?

Nighttime leaking specifically is typical of urinary sphincter mechanism incompetence (USMI) a condition where the urethral sphincter relaxes during sleep or rest.

If this is new after surgery, anesthesia and opioid medications may have temporarily worsened underlying borderline sphincter function.

If it continues beyond 2 to 3 weeks, a vet visit for urinalysis and discussion of phenylpropanolamine (PPA) or other treatment is appropriate.

How do I know if my dog has a UTI after TPLO?

Signs of UTI include: cloudy or bloody urine, strong or unusual odor, frequent small amounts of urination, straining to urinate, and licking at the genital area more than normal.

Some dogs with UTI also show lethargy and decreased appetite. Urinalysis and culture confirm the diagnosis.

Should I limit my dog's water intake to reduce accidents?

No. Do not restrict water. Hydration is important for recovery and kidney function. Restricting water can concentrate the urine and increase UTI risk.

Instead, manage accidents through scheduled outdoor trips and waterproof bedding.

Resources

• VCA Animal Hospitals. Tibial Plateau Leveling Osteotomy (TPLO) in Dogs. vcahospitals.com
• ACVS. Cranial Cruciate Ligament Disease. acvs.org
• PetMD. Urinary Incontinence in Dogs. petmd.com
• Midwest Veterinary Specialists. Post-Operative Care Following TPLO. midwestveterinaryspecialists.com

"Failure rate" is used loosely when owners discuss TPLO, which can cause significant confusion. A complication is not the same as a failure.

Understanding what the published data actually shows and distinguishing minor complications from true surgical failures gives owners a much clearer picture of what to expect.

Quick answer: The overall TPLO complication rate is 10 to 34% across studies; most are minor. Major complications requiring reoperation occur in 2 to 7%. Infection is the most common major complication. Long-term good outcomes are reported in 90 to 93% of dogs.

Key takeaways

• Overall complication rate is 10 to 34% across published studies; most complications are minor and resolve without additional surgery
• Major complication rate requiring reoperation is 2 to 7%: a 1,000-dog study found 14.8% overall with 6.6% major complications
• SSI is the most common major complication: 2.9% to 25.9% across studies; giant breeds over 50 kg are at highest risk
• Small dogs under 15 kg have significantly lower complication rates: 4.44% in one 90-dog study, with no revisions
• Good to excellent long-term outcomes in 90 to 93% of dogs: the complication rate does not equal the failure rate
• Surgeon experience is the most modifiable risk factor: complication rates are consistently lower at high-volume specialty centers with board-certified surgeons

Defining "failure" vs. "complication"

This distinction is critical for interpreting the literature and for setting owner expectations accurately.

Complication: any deviation from the expected post-operative course. This includes minor findings like superficial wound dehiscence, mild swelling, or radiographic evidence of delayed osteotomy healing with no clinical signs. Many publications include these minor events in their complication rates.

Major complication: an event requiring additional surgical intervention or causing extended lameness. Major complications represent the subset of complications that meaningfully affect recovery and outcome.

Failure: the most restrictive definition surgery that did not achieve its goal of stifle stabilization, resulting in persistent instability and requiring revision with a different technique. True failure in this sense is uncommon after TPLO.

What published complication data shows

Overall complication rates

Vetamac confirms: complication rates following TPLO surgery range from 14% to 34%, with less than 10% of cases requiring a second surgery.

PMC (intraoperative bacterial culture study) confirms: the complication rate of TPLO varies between 10% and 34%, with 2 to 4% requiring surgical revision.

Today's Veterinary Practice reports a 14.8% complication rate in 1,000 TPLO patients (6.6% major — requiring repeat surgery or extended lameness), including 2.8% late meniscal injury and 6.6% infections.

Infection rates

Infection is the most common major complication and the one with the greatest variation by dog size and surgical setting.

PMC confirms: SSI rate after TPLO is reported to be 2.9% to 25.9% across studies, which is higher than other clean orthopedic surgeries (2.0 to 6.7%).

Surgical site infection rates of 21.3% to 25.9% have been reported specifically for giant-breed dogs weighing over 50 kg.

The implant removal rate due to infection is 3 to 7.4% per published literature (PMC PRP study; ResearchGate implant removal study).

Complication rates by dog size

Dog size is a consistent predictor of complication risk.

PLOS One retrospective (90 dogs under 15 kg): overall complication rate 4.44%, with no complications requiring surgical revision.

The study confirms: the complication rate in dogs under 15 kg is less than that historically reported in heavier dogs.

PubMed retrospective (small and medium dogs, 2.0 and 2.7 mm plates): overall complication rate 36%.

The most common complications were radiographic evidence of delayed healing (9%), patellar tendon thickening (8%), and tibial tuberosity fracture (6%). Only 7% of complications were major.

PLOS One confirms: the TPLO complication rates range from 10% to 34% and vary in severity from swelling and bruising to fractures and osteomyelitis.

Implant-related complications reportedly occur in under 10% of all TPLO procedures.

Long-term success rates

Complication rates must be interpreted alongside long-term success rates.

The retrospective cohort study comparing TPLO, Tightrope, and TTA found: function greater than 1 year after surgery was 93.1% for TPLO, 92.7% for Tightrope, and 89.2% for TTA.

SustainableVet.org confirms: good to excellent long-term outcomes are achieved in 90.4% of patients up to 6.8 years after TPLO surgery; 80 to 90% of owners are satisfied with their dog's long-term recovery.

A dog can have a complication even a significant one like an infection and still achieve a good long-term outcome after the complication is resolved.

The complication rate and the long-term success rate address different aspects of the outcome.

Factors that affect complication and failure rates

Surgeon experience and volume

This is the most consistently cited modifiable risk factor. High-volume specialty centers and board-certified surgeons consistently report lower complication rates than general practitioners performing occasional TPLO procedures.

Surgical efficiency, technique precision, and post-operative protocol standardization all contribute.

Dog size and body weight

Larger dogs generate higher joint forces, have larger dead space at the surgical site, and place more mechanical demand on the implant during healing.

These factors contribute to the higher complication rates seen in large and giant breeds.

Excessive tibial plateau angle (TPA)

Dogs with TPA above 35 degrees (excessive TPA, or eTPA) have higher complication rates.

Today's Veterinary Practice notes: owner-perceived outcome was superior for eTPA group dogs when TPLO resulted in TPA of 14 degrees or less compared to those with TPA greater than 14 degrees.

Postoperative complications were more common in dogs with eTPA.

Post-operative activity restriction compliance

Dogs that are over-active during recovery have higher rates of implant complications, seroma formation, and wound complications.

Strict adherence to the prescribed restriction protocol is the owner's primary contribution to reducing complication risk.

For the complications overview, see 15 common complications after TPLO surgery in dogs. For the infection signs guide, see TPLO plate infection signs and treatment.

For the long-term outcomes guide, see long-term outcomes of TPLO surgery. For the plate removal guide, see TPLO plate removal recovery guide.

Frequently asked questions

What is the TPLO failure rate?

Depends on how "failure" is defined. If failure means any complication: 10 to 34% across studies. If failure means major complications requiring surgery or causing extended lameness: 2 to 7%.

If failure means persistent instability requiring revision with a different technique: uncommon and not consistently reported across large series.

Is TPLO safe for large breed dogs?

Yes, but with a higher complication risk than small dogs. Vetamac confirms: for large breeds, TPLO is still the gold standard, providing better long-term stability than alternatives.

The higher complication rate in large dogs reflects the greater mechanical demands and surgical challenges, not a fundamental unsafety of the procedure.

What percentage of TPLO dogs need a second surgery?

Across published studies, 2 to 10% require a second surgical intervention. Most second surgeries address infection (requiring plate removal), late meniscal tears (requiring partial meniscectomy), or implant complications.

Does my dog's vet experience affect failure rate?

Yes, substantially. Surgeons performing fewer than a set number of TPLO procedures per year have higher complication rates than high-volume specialists.

This is one reason referral to a board-certified orthopedic surgeon (ACVS diplomate) is recommended for TPLO.

If my dog has a complication, does that mean the TPLO failed?

Not necessarily. Many dogs who develop complications including infections requiring plate removal still achieve good to excellent long-term function after the complication is resolved.

The complication rate and the long-term outcome are different measures.

Resources

• Today's Veterinary Practice. Canine Cranial Cruciate Disease: Evidence-Based Look at Current Treatment Modalities. todaysveterinarypractice.com
• PLOS One. Risk Factors for Short-Term Postoperative Complications in Dogs Weighing Less Than 15 kg. journals.plos.org
• PubMed. Short-Term Complications Associated With TPLO in Dogs Using 2.0 and 2.7 mm Plates. pubmed.ncbi.nlm.nih.gov
• PMC. Clinical Relevance of Positive Intraoperative Bacterial Culture in TPLO in Dogs. ncbi.nlm.nih.gov
• Vetamac. TPLO Surgery for Dogs: Success Rates and Alternative Options. vetamac.com

CCL rupture in dogs is not the same injury as ACL rupture in humans.

In humans, the anterior cruciate ligament typically tears during sudden trauma a pivoting fall on a ski slope, a tackle on a football field.

In dogs, the same ligament almost always fails through slow, progressive degeneration that began months or years before the day the dog comes in lame.

Understanding why the canine CCL fails and which dogs are most at risk is essential for prevention strategies and for recognizing early warning signs.

Quick answer: The canine CCL fails through progressive degeneration, not sudden trauma. Key risk factors are breed, obesity, poor fitness, tibial slope, and genetics. At least 50% of dogs that rupture one CCL will rupture the other within 1 to 2 years.

Key takeaways

• CCL rupture results from degeneration, not trauma: ACVS confirms slow, progressive degeneration rather than acute injury to a healthy ligament
• Obesity is the most modifiable risk factor: excess weight increases compressive and shear forces on the CCL with every step
• High-risk breeds include Labrador, Rottweiler, Newfoundland, Mastiff, and Akita: genetic inheritance has been demonstrated in Newfoundlands and Labradors
• Partial tears almost always progress to complete rupture: ACVS confirms this and notes progression is the rule, not the exception
• At least 50% of dogs rupture the opposite CCL within 1 to 2 years of the first rupture
• Neuter status increases CCL risk: spayed and neutered dogs show higher rates in multiple studies

Why dog CCL disease differs from human ACL injury

Colorado State University: "In humans, trauma (such as skiing, football, or soccer injuries) is the most common reason for injury of the ACL.

This 'traumatic' rupture can happen in dogs but is quite rare."

CSU: "Most commonly, CCLD is caused by a combination of many factors, including aging of the ligament (degeneration), obesity, poor physical condition, conformation, and breed."

In humans, a healthy ACL tears from a single high-energy event. In dogs, the ligament is already weakened before it ruptures.

The moment of obvious lameness is the endpoint of a months-long degenerative process.

ACVS: ligament rupture is "the result of subtle, slow degeneration that has been taking place over a period of time rather than the result of sudden trauma to an otherwise healthy ligament."

Fitzpatrick Referrals: "In the vast majority of dogs, the CrCL ruptures as a result of long-term degeneration, whereby the fibres weaken and fray over time, losing their structure and function."

The main causes and risk factors

Degeneration (aging and immune-mediated)

The underlying degenerative process in CCL disease involves progressive breakdown of collagen fibers within the ligament.

PMC (Cranial Cruciate Ligament Rupture Review): "The structural weakening of this joint due to the progressive degeneration of the ligament is the most accredited etiopathogenetic hypothesis."

The degeneration appears to involve both mechanical fatigue and immune-mediated inflammatory processes within the joint.

Synovitis (joint inflammation) often precedes complete rupture and may be detected during veterinary examination before full failure occurs.

Breed and genetics

ACVS: "Certain dog breeds are known to have a higher incidence: Rottweiler, Newfoundland, Staffordshire Terrier, Mastiff, Akita, Saint Bernard, Chesapeake Bay Retriever, and Labrador Retriever."

ACVS: "A genetic mode of inheritance has been shown for Newfoundlands and Labrador Retrievers."

Fitzpatrick Referrals: "Genetic factors are likely very important, with certain breeds being predisposed including Labradors, Rottweilers, Boxers, West Highland White Terriers, and Newfoundlands."

Breeds with low CCL disease incidence include Greyhounds, Dachshunds, Basset Hounds, and Old English Sheepdogs.

Fitzpatrick: "Supporting evidence for a genetic cause was obtained by assessment of family lines and the knowledge that many animals rupture both knees relatively early in life."

Obesity

ACVS: "Poor physical body condition and excessive body weight are risk factors for the development of CrCLD. Both of these factors can be influenced by pet owners."

PMC: "A predisposing factor is obesity, in which the concentrations of circulating inflammatory mediators increase, such as the concentrations of pro-inflammatory adipokines released from adipose tissue, which may contribute to degenerative phenomena."

Obesity matters in two ways: it increases the mechanical load on the CCL with every step, and it elevates systemic inflammation, which accelerates ligament degeneration.

A dog 10% overweight places significantly more stress on both stifle joints with every stride.

Tibial plateau angle (conformation)

The tibial plateau is the top surface of the tibia. In dogs, it slopes caudally. During weight-bearing, this slope creates a cranial shear force on the tibia that the CCL normally resists.

Fitzpatrick: "Increased tibial plateau angle (backwards slope at the top of the tibia) may play a role" in CCL disease.

Dogs with steeper tibial plateau angles experience greater cranial thrust with each step, increasing CCL load.

This is why TPLO and CBLO surgery (which reduce the tibial plateau angle) neutralize the instability rather than replacing the torn ligament.

Neuter status

Multiple studies have found that spayed and neutered dogs have higher rates of CCL disease than intact dogs. The relationship is stronger in some breeds than others.

Proposed mechanisms include the loss of sex hormones that influence joint development and ligament maturation, longer bone growth periods in dogs neutered before skeletal maturity, and altered body composition.

Contralateral (opposite knee) risk

NCBi (Radiographic Risk Factors study): "Among dogs presented with unilateral CCL rupture, a large proportion will develop contralateral CCL rupture within 12 to 24 months of initial diagnosis.

This risk is in the range of 22 to 54% at 6 to 17 months of diagnosis."

CSU: "At least half of the dogs that have a cruciate ligament problem in one knee will likely, at some future time, develop a similar problem in the other knee."

This bilateral risk reflects the systemic nature of CCL degeneration both ligaments are affected by the same genetic, hormonal, and conformation factors.

Partial tears: the warning stage

The CCL typically does not rupture all at once. Partial tears are common and produce intermittent hind limb lameness that owners sometimes attribute to a sprain.

CSU: "Partial tearing of the CCL is common in dogs and frequently precedes complete rupture."

ACVS: "Partial tearing of the CCL is common in dogs and almost always progresses to a full tear over time."

A dog with a partial CCL tear that receives cage rest and returns to activity will almost always eventually progress to complete rupture.

Surgical intervention at the partial tear stage can be considered for active dogs, though evidence on whether it prevents eventual complete rupture is limited.

Signs of CCL disease

• Hind limb lameness, especially after exercise
• Sudden onset of non-weight-bearing on a back leg
• Stiffness when getting up, especially after rest
• Muscle atrophy on the affected hind limb
• Thickening on the inside of the knee joint (medial buttress)
• Positive cranial drawer test or tibial compression test on orthopedic examination

Can CCL tears be prevented?

Risk cannot be eliminated in predisposed breeds, but it can be reduced.

ACVS: "Consistent physical conditioning with regular activity and close monitoring of food intake to maintain a lean body mass is advisable."

Evidence-based prevention strategies:

• Maintain healthy body weight (most impactful modifiable factor)
• Consistent, regular exercise rather than intermittent intense activity
• Avoid sudden load increases (the "weekend warrior" pattern)
• Discuss neutering timing with your vet, particularly in high-risk breeds

For the surgical treatment of CCL rupture, see CBLO surgery in dogs: cost, recovery, and success rate. For the surgery vs. conservative management decision, see canine cruciate injuries: surgery vs. conservative management.

For meniscal injury that often accompanies CCL tears, see torn meniscus surgery cost in dogs. For when CCL disease requires specialist referral, see when to refer for orthopedic surgery.

Frequently asked questions

My dog tore its CCL running in the yard. Wasn't that traumatic?

The event may have looked sudden, but the ligament was almost certainly already degenerated.

ACVS: the rupture is "the result of subtle, slow degeneration... rather than sudden trauma to an otherwise healthy ligament." The yard run was the last straw, not the cause.

Which dog breeds are at highest risk for CCL tears?

ACVS identifies Rottweilers, Newfoundlands, Staffordshire Terriers, Mastiffs, Akitas, Saint Bernards, Chesapeake Bay Retrievers, and Labrador Retrievers as high-incidence breeds. Fitzpatrick Referrals adds Boxers and West Highland White Terriers.

Does obesity really make that much difference?

Yes. Obesity increases both mechanical load on the CCL and systemic inflammation via adipokines from fat tissue.

It is the most modifiable risk factor maintaining healthy body weight is the single most impactful thing an owner can do for CCL disease prevention.

My dog had surgery on one knee. How long before the other goes?

NCBi data: the risk of contralateral CCL rupture is 22 to 54% within 6 to 17 months of the first diagnosis. Monitoring the other knee closely after the first diagnosis is important.

Maintaining lean body weight and avoiding abrupt increases in activity are the main protective strategies.

Can a dog with a partial CCL tear be managed without surgery?

Conservative management (rest, weight loss, physical therapy) may be attempted for partial tears, particularly in small dogs. But ACVS states partial tears "almost always progress to a full tear over time."

Discuss with an orthopedic specialist whether surgery at the partial tear stage is appropriate for your dog.

What is the difference between CCL and ACL?

CCL (cranial cruciate ligament) is the correct term in dogs; ACL (anterior cruciate ligament) is the human equivalent. They are anatomically similar structures that stabilize the knee joint.

The key clinical difference: in humans, ACL tears are usually traumatic; in dogs, CCL tears are almost always degenerative.

Resources

• ACVS. Cranial Cruciate Ligament Disease. acvs.org
• CSU Veterinary Health System. Canine Cruciate Ligament Injury. vetmedbiosci.colostate.edu
• Fitzpatrick Referrals. Cruciate Ligament Disease or Injury. fitzpatrickreferrals.co.uk
• NCBi PMC. Radiographic Risk Factors for Contralateral Rupture in Dogs with Unilateral CCL Rupture. ncbi.nlm.nih.gov
• PMC. Cranial Cruciate Ligament Rupture in Dogs: Review on Biomechanics, Etiopathogenetic Factors and Rehabilitation. ncbi.nlm.nih.gov