Zlig (STIF-VETLIG) is an intra-articular synthetic implant used to reconstruct the cranial cruciate ligament inside the joint a conceptually different approach from TPLO, which changes joint mechanics rather than replacing the ligament.

Both are valid surgical options for CCL rupture in dogs, and the evidence base for Zlig, while smaller than for TPLO, is growing.

Quick answer: Zlig replaces the torn CCL inside the joint using a synthetic fiber implant through small bone tunnels. A 107-case prospective study reported good to excellent results in 97 cases. TPLO has a much larger evidence base and is the ACVS first-choice for large dogs.

Key takeaways

• Zlig reconstructs the CCL inside the joint using a synthetic fiber implant through small bone tunnels; TPLO changes joint geometry instead
• A 107-case prospective study reported good to excellent results in 97 cases: the largest Zlig dataset, single-centre, without controlled TPLO comparison
• TPLO has a significantly larger evidence base: 25+ years of RCTs and ACVS first-choice status for dogs over 60 lbs
• Zlig requires only small bone tunnels, no osteotomy: bone-cutting complications such as delayed union are not relevant
• Implant failure is the primary Zlig-specific risk: the synthetic ligament may stretch or fail over time in large or very active dogs
• Zlig suits bilateral CCL cases in small to medium dogs: both knees can sometimes be addressed in one procedure

How Zlig works

Zlig stands for Z-Ligament. The procedure uses a synthetic fiber implant (marketed as STIF-VETLIG GLOBAL) placed intra-articularly inside the joint capsule to replace the torn CCL.

Unlike extracapsular techniques (lateral suture, Tightrope) which place material outside the joint, Zlig anatomically reproduces the CCL's position within the joint.

The procedure involves drilling small bone tunnels through the femur and tibia at the anatomical insertion points of the CCL.

The synthetic implant is passed through these tunnels and secured, providing immediate mechanical stability similar to the original ligament.

Because there is no bone cutting or tibial rotation, Zlig is less invasive than TPLO and significantly faster to perform.

Recovery may be faster in the early post-operative period for the same reason.

The hund-kreuzbandriss.de clinical commentary (German veterinary reference site) notes: TPLO is a fairly invasive technique that causes irreversible changes.

Intra-articular reconstruction with synthetic fibers only requires small bone tunnels, and complications from osteotomy when they occur are not always easy to correct.

Who makes the Zlig implant?

The Zlig system uses the STIF-VETLIG GLOBAL implant, manufactured in France.

The procedure was developed primarily in France and Germany. It is gaining awareness in other countries but remains far less available than the major TPLO systems.

The highly porous intra-articular fiber design promotes fibroblast penetration and collagen fiber ingrowth over time, which the manufacturers propose increases implant longevity by improving resistance to flexion and torsional forces.

What the evidence shows

Primary Zlig outcome study

A prospective study by Le Doze, Paris, and Pages (2012 to 2021, 107 cases) found good to excellent results in 97 of 107 cases.

The study was conducted at two veterinary clinics in France. This is the most comprehensive Zlig-specific outcome dataset in the veterinary literature.

The hund-kreuzbandriss.de review confirms: Reconstruction of the CCL using the intra-articular synthetic implant STIF-VETLIG GLOBAL leads to good to excellent results in 97 cases in this prospective study from 2012 to 2021.

Limitations of current Zlig evidence

• The primary study is single-centre, non-randomized, and lacks a direct comparison control group
• Long-term data beyond the study's follow-up period is limited
• The procedure has not been evaluated in large-scale randomized controlled trials comparable to those available for TPLO and TTA
• The evidence base is substantially smaller than for TPLO (25+ years of multi-centre data)

TPLO evidence in context

TPLO has been evaluated in prospective randomized studies, force plate gait analysis trials, and multi-year cohort studies across dozens of institutions.

The ACVS recommends TPLO as the most commonly performed procedure for dogs over 60 lbs based on this evidence base.

Zlig vs TPLO: key differences

Patient selection

Zlig may be preferred when:

• Small to medium breed dogs (primary candidate group in current evidence)
• Bilateral CCL rupture in a small dog where simultaneous correction in one anaesthesia event is desired
• Dog owner prefers to avoid the irreversible tibial changes of an osteotomy
• The surgeon is specifically trained in the Zlig technique

TPLO is typically recommended when:

• Dogs over 30 to 40 lbs, especially large and giant breeds
• Dogs with steep tibial plateau angle (TPA) some are not suitable candidates for Zlig due to concurrent patellar luxation or excessive tibial ridge concavity
• The ACVS first-choice recommendation is preferred, with the largest evidence base
• General specialty practice context where Zlig expertise is not available

Hund-kreuzbandriss.de notes: dogs with a steep tibial plateau angle, concurrent patellar luxation, or excessive concavity of the tibial ridge are not good candidates for Zlig.

In these cases, TPLO represents an excellent and often the only alternative.

For the full surgical alternatives overview, see alternatives to TPLO surgery for dogs. For the TPLO vs Tightrope comparison, see Tightrope vs TPLO surgery for dogs.

Frequently asked questions

Is Zlig as effective as TPLO?

For small to medium dogs, the single-centre prospective study shows good to excellent results in the majority of cases.

A direct head-to-head randomized comparison with TPLO in matched patient populations has not been published, so direct effectiveness comparison is not currently possible.

TPLO has a much stronger and broader evidence base overall.

Can large dogs have Zlig surgery?

The current evidence base for Zlig is strongest in small to medium dogs. Large dogs generate higher joint forces that place more demand on the synthetic implant over time.

Many surgeons with Zlig experience reserve it for smaller patients, though there is no absolute size cutoff in the literature.

What happens if the Zlig implant fails?

The synthetic ligament can stretch or rupture over time. If this occurs, the stifle returns to instability and lameness.

Revision surgery would typically involve a different approach TPLO or TTA since the anatomy has not been altered by the Zlig procedure, making revision more straightforward than after an osteotomy.

How long does Zlig surgery take?

Shorter than TPLO in most cases, because no osteotomy is performed.

The exact duration varies by surgeon experience and patient anatomy, but the minimally invasive nature of the procedure is one of its practical advantages.

Where can I find a surgeon who performs Zlig?

Zlig is performed by veterinary surgeons specifically trained in the technique, primarily in France and Germany where the procedure was developed, and increasingly in other countries.

Board-certified veterinary orthopedic surgeons can advise whether the technique is available in your region.

Resources

• Hund-Kreuzbandriss. Zlig Method: A Study. (Le Doze et al., 2012 to 2021 prospective study summary.) hund-kreuzbandriss.de
• Hund-Kreuzbandriss. TPLO vs TTA vs ZLig vs Suture Retraction: 6 Methods. hund-kreuzbandriss.de
• ACVS. Cranial Cruciate Ligament Disease. acvs.org
• Vetamac. TPLO Surgery for Dogs: Success Rates and Alternative Options. vetamac.com

CCL (cranial cruciate ligament) rupture is one of the most common orthopedic injuries in dogs.

Canine CCL rupture often develops gradually through progressive degeneration. Early signs are subtle and easy to dismiss as aging or a minor sprain.

Recognizing the signs early improves outcomes because partial tears can progress to complete ruptures if not addressed.

Quick answer: Common signs a dog may need TPLO surgery: persistent rear limb limping, stiffness after rest, toe-touching gait, sitting with one rear leg extended (positive sit test), stifle swelling and warmth, and sudden non-weight bearing. A drawer test and radiographs confirm CCL rupture.

Key takeaways

• Hind limb lameness is the most common presenting sign: any dog with a persistent rear leg limp warrants veterinary evaluation; CCL rupture is the most common orthopedic cause
• The classic sitting posture change is highly specific: a dog now sitting with one rear leg extended to the side rather than tucked under is compensating for stifle pain (positive sit test)
• Intermittent lameness that comes and goes may indicate a partial tear: partial tears progress to complete ruptures in most dogs without treatment
• Stiffness after rest or sleep is a common early sign: the dog seems fine after moving around but is stiff when first rising
• Non-weight bearing or acute severe lameness after activity indicates a complete CCL rupture; the dog holds the leg entirely off the ground
• Both stifles are at risk: 30 to 40% of dogs develop CCL rupture in both knees over time; monitor the opposite side in any dog with known CCL disease

The 13 signs

1. Hind limb limping after exercise

The dog walks normally at rest but limps noticeably after running, playing, or climbing stairs. The limping may resolve after 10 to 30 minutes of rest.

This pattern suggests the joint can handle low-level loading but is symptomatic under increased mechanical stress.

SustainableVet.org confirms: occasional limping may come and go, especially after exercise or long walks; some days may seem better than others, but this inconsistency is a sign of joint problems.

2. Toe-touching gait (barely bearing weight)

The dog walks with most weight on three legs, barely resting the toes of the affected rear limb on the ground.

The toe touches down for stability and ground contact but carries almost no weight.

SustainableVet.org confirms: the dog may lightly place just the toes of the affected leg on the ground without putting full weight on it; this is a common sign of knee pain.

Coldwater Online confirms: sitting with the leg kicked out to the side is a classic signal.

3. Sitting with one rear leg extended to the side (positive sit test)

A dog with stifle pain cannot comfortably flex the knee to a normal sitting position. Instead, the affected leg extends out to the side while the dog sits.

This is reproducible and highly suggestive of stifle pathology.

AESC confirms: dogs with CCL tears often sit with one leg stuck out to the side rather than tucked normally.

4. Stiffness after rest or sleep

The dog gets up from sleeping or lying and is noticeably stiff and lame for the first few minutes. After moving around, the stiffness resolves.

This is the classic pattern of joint inflammation: fluid redistribution during rest causes stiffness that is mobilized by movement.

Coldwater Online confirms: stiffness after rest, especially in the morning or after a nap, is a classic early signal.

5. Reluctance to go up or down stairs

Climbing stairs requires repetitive stifle flexion and load bearing. A dog with a partial or complete CCL tear shows hesitation or refusal to use stairs, often pausing at the base or top.

6. Reluctance to jump into the car or onto furniture

Loading into the car from the ground requires a pushing-off motion from the rear legs with sudden stifle extension. Dogs with CCL pain become reluctant to perform this movement.

7. Muscle atrophy of the rear leg

The quadriceps and hamstring muscles of the affected leg visibly reduce in size compared to the opposite leg. This occurs because the dog guards the painful limb and reduces loading over time.

Noticeable asymmetry in thigh circumference is a sign of chronic or progressive CCL disease.

8. Swelling at the stifle joint

The stifle (knee) joint becomes palpably enlarged.

The medial compartment (inside of the knee) often shows a visible soft tissue swelling called a medial buttress -- fibrous tissue that develops in response to chronic joint instability.

The joint may feel warm compared to the opposite stifle.

MetLife Pet Insurance confirms: the stifle area may appear swollen or feel warm to the touch.

9. Audible popping or clicking from the knee

Meniscal damage accompanies CCL rupture in approximately 40 to 60% of chronic cases.

When the unstable tibia slides across the femoral condyles, it may crush or tear the meniscus, producing an audible clicking or popping sound.

AESC confirms: popping noises as the knee joint moves may be heard and are a sign of possible meniscal involvement.

10. Sudden complete non-weight bearing after activity

The dog was running, playing, or jumping, then suddenly cried out and completely stopped using the rear leg. This acute presentation indicates a sudden complete CCL rupture.

Unlike gradual partial tears, complete acute ruptures are painful and dramatic at onset.

Sandringham Vet confirms: most dogs with a CCL tear will avoid putting weight on the affected leg; difficulty standing up or sitting from a resting position is common after complete rupture.

11. Chronic intermittent lameness with improvement then worsening

The dog limps, seems to improve, then worsens again. This cyclical pattern often reflects a partial tear progressing with activity then settling with rest.

Without treatment, partial tears progress to complete ruptures in most dogs.

12. Both rear legs showing signs simultaneously

Some dogs present with bilateral CCL disease -- both stifles partially or completely ruptured.

These dogs show a characteristic bunny-hopping gait (using both rear legs together rather than alternating) or severe difficulty rising.

Midvalley Animal Clinic notes 30 to 40% of patients will develop CCL rupture in both knees over time.

13. Hindquarters weakness or instability during activity

The dog's rear end seems weak or gives way during turning, running, or on uneven terrain. This reflects dynamic instability of the stifle under load rather than pain at rest.

How the diagnosis is confirmed

Signs alone are not sufficient for definitive diagnosis. Veterinary confirmation requires:

Physical examination tests

Tibial thrust test: the vet applies cranial-directed force to the hock while stabilizing the femur. In a CCL-deficient stifle, the tibia slides forward under this force.

Drawer test: with the dog sedated or relaxed, the vet grasps the femur and tibia and attempts to slide them in opposite directions. Forward movement of the tibia relative to the femur (cranial drawer) confirms CCL rupture.

Chewy confirms: your veterinarian will check for tibial thrust -- abnormal sliding of femur and tibia. A positive drawer test confirms CCL rupture is very likely.

Radiographs

X-rays assess joint fluid accumulation (which causes fat pad displacement on the lateral view -- the "fat pad sign"), early arthritis changes, and tibial plateau angle (TPA) measurement for surgical planning.

Radiographs do not directly image the CCL but confirm the secondary changes of CCL disease.

Arthroscopy or arthrotomy

At the time of surgery, the surgeon directly inspects the CCL and menisci. This provides the definitive diagnosis and allows concurrent meniscal treatment.

For the TPLO surgery overview, see what causes TPLO surgery to be needed in dogs. For alternatives, see alternatives to TPLO surgery for dogs.

For TPLO vs lateral suture, see lateral suture vs TPLO for dogs. For surgery preparation, see preparing for your dog's TPLO surgery.

Frequently asked questions

Can a dog with a CCL tear recover without surgery?

Partial tears in very small dogs (under 10 to 15 kg) sometimes stabilize with strict rest and conservative management.

For most dogs, particularly those over 15 to 20 kg, conservative management does not restore normal joint stability and the lameness persists or worsens.

Complete ruptures in any dog over about 15 kg typically require surgery for full functional recovery.

How quickly does a CCL tear progress if untreated?

A partial tear typically progresses to a complete rupture within weeks to months if activity is not restricted. Arthritis develops progressively from the moment the joint becomes unstable.

Early treatment reduces arthritis progression and improves long-term outcomes.

My dog limped once and then seemed fine. Should I go to the vet?

Yes, if the limp was in a rear leg and involved guarding or reduced weight bearing. A single episode of rear limb lameness lasting more than a few minutes warrants evaluation.

Early CCL tears can produce episodic lameness that resolves with rest -- evaluation while the dog appears normal can still reveal joint instability or effusion on examination.

Does the dog need sedation for the drawer test?

Sedation often improves accuracy. A dog in pain or a large, tense dog may resist examination sufficiently to produce a false-negative drawer test.

Sedation allows full relaxation and more reliable assessment of drawer and tibial thrust.

Which breeds are most at risk for CCL rupture?

Dispomed confirms high-risk breeds include Rottweilers, Newfoundlands, Staffordshire Terriers, Mastiffs, Akitas, Saint Bernards, Labrador Retrievers, and Chesapeake Bay Retrievers. Neutered dogs are at higher risk than intact dogs of the same breed.

Obesity and poor physical condition also increase risk.

Resources

• SustainableVet. 13 Signs Your Dog May Need TPLO Surgery. sustainablevet.org
• AESC Parker. TPLO Surgery in Dogs: Frequently Asked Questions. aescparker.com
• MetLife Pet Insurance. TPLO Surgery for Dogs. metlifepetinsurance.com
• ACVS. Cranial Cruciate Ligament Disease. acvs.org

Some degree of lameness after TPLO surgery is expected. The surgery involves a bone cut and plate fixation, and the dog's leg needs weeks to heal.

The clinical challenge for owners is distinguishing between normal post-surgical lameness (which requires patience) and lameness that indicates a complication (which requires prompt veterinary attention).

The answer depends heavily on timing, trajectory, and accompanying signs.

Quick answer: Normal post-TPLO lameness should show consistent week-over-week improvement. The most common pathological causes are: surgical site infection, late meniscal tear, implant loosening, muscle atrophy, delayed bone healing, and progressive osteoarthritis. The key signal is trajectory reversal -- lameness worsening after improvement or failing to improve for 2 or more weeks.

Key takeaways

• Some lameness is normal throughout the first 8 to 12 weeks of TPLO recovery: mild limping that improves gradually over 6 to 12 weeks is typical; the key variable is trajectory
• Trajectory reversal is the key warning sign: lameness that worsens after improvement, or fails to improve for 2 or more consecutive weeks, warrants veterinary evaluation before the next appointment
• Late meniscal tear is a recognized cause of sudden lameness regression: recurrence of lameness after initial resolution can indicate meniscal injury; it occurs in 2 to 22% of TPLO cases
• Muscle atrophy is a commonly underappreciated cause of persistent lameness: the affected leg loses muscle mass during restriction; inadequate rehabilitation leaves an asymmetric gait
• Progressive osteoarthritis is the most common cause of chronic mild lameness starting months after surgery; TPLO slows but does not stop this process
• Implant failure and infection must be ruled out for lameness that is worsening or not responding to conservative management; radiographs and culture are required for diagnosis

Normal post-surgical lameness: what to expect

Week 1 to 2

Most dogs are significantly lame in the first 1 to 2 weeks. They may toe-touch only or hold the leg off the ground entirely.

This is the acute post-surgical inflammatory phase combined with the effects of anesthesia wearing off.

SustainableVet.org confirms: some lameness is expected after TPLO surgery, especially in the first few weeks; normal recovery lameness is mild limping that improves gradually over 6 to 12 weeks.

Week 2 to 6

Consistent improvement should be visible week over week. By week 4, most dogs should be bearing significant weight on the operated leg during slow walking.

Three-legged walking during activity is still common but should be decreasing.

Week 6 to 12

Most dogs should be consistently weight-bearing on the operated leg. By week 12, most are nearly normal for household activities.

Radiographic confirmation of bone healing at weeks 6 to 8 and 12 guides when activity can increase.

Pathological causes of post-TPLO lameness

1. Surgical site infection (SSI)

Timing: most commonly weeks 1 to 4, but can occur at any stage (including months later for deep implant-associated infections).

Mechanism: bacterial contamination of the incision or implant causes inflammation and pain at the plate site, which produces or worsens lameness.

Signs accompanying lameness: redness, warmth, swelling, or discharge at the incision or plate site.

Action required: same-day veterinary contact for any infection signs alongside lameness.

2. Late meniscal tear

Timing: typically weeks 4 to 12 post-surgery, though it can occur months later.

Mechanism: the meniscus, which may have been structurally weakened before surgery or had a small tear not detected at surgery, fails under load during the recovery period.

Signs accompanying lameness: audible or palpable meniscal click; pain on stifle manipulation; sudden lameness regression in a dog that had been improving.

Animal Outpatient Surgery confirms: if lameness resolves after TPLO and recurs at a later time, this can be an indication of meniscal injury.

Action required: veterinary evaluation within 24 to 48 hours; arthroscopy or arthrotomy for diagnosis and partial meniscectomy for treatment.

3. Implant loosening or failure

Timing: most common in the first 6 to 12 weeks when the osteotomy is still healing and the plate bears the full load. Can also occur later from chronic infection or late trauma.

Mechanism: excessive activity before the osteotomy heals applies forces that exceed the plate's tolerance; screws pull out or the plate bends.

Signs accompanying lameness: sudden severe lameness; pain at the plate site; sometimes audible clicking or grinding; radiographic evidence of screw loosening or plate migration.

SustainableVet.org confirms: signs of implant failure include ongoing limping, pain, swelling around the implant site, and unusual clicking or grinding sounds from the joint.

Action required: same-day emergency veterinary contact for sudden severe lameness; radiographs urgently required.

4. Muscle atrophy and weakness

Timing: most prominent from weeks 4 to 12; persists for months if rehabilitation is inadequate.

Mechanism: during activity restriction, the operated leg muscles (quadriceps, hamstrings, hip extensors) atrophy rapidly. Asymmetric muscle mass leads to asymmetric weight distribution and abnormal gait patterns that present as persistent limping.

Vetplayas confirms: limited mobility during recovery leads to muscle loss and decreased strength. This imbalance results in abnormal gait patterns and subsequent limping.

Signs: visible muscle asymmetry (operated thigh smaller than opposite); lameness that worsens with activity and improves with rest; no accompanying warmth, redness, or plate-site changes.

Action required: rehabilitation assessment; physiotherapy to rebuild muscle mass.

5. Delayed bone healing

Timing: identified at the 6 to 8 week radiographic assessment.

Mechanism: the osteotomy is not showing expected callus formation and cortical bridging. Common causes include infection, excessive activity, poor blood supply, or systemic factors (NSAIDs at high dose for extended periods, nutritional deficiencies).

Signs: persistent lameness at a level that does not match the expected trajectory; confirmed radiographically.

Action required: veterinary investigation for underlying cause; extended activity restriction; sometimes additional diagnostics (culture to rule out occult infection).

6. Delayed union or non-union

Timing: identified at 12+ weeks when bone healing should be complete.

Mechanism: the osteotomy fails to heal. The plate is subject to continued cyclic loading without the protection of consolidated bone, increasing implant failure risk.

Action required: specialist reassessment; may require bone grafting, implant revision, or extended medical management.

7. Progressive osteoarthritis

Timing: typically becomes clinically apparent after 6 to 12 months.

Mechanism: CCL disease initiates an irreversible arthritis process in the stifle. TPLO reduces but does not eliminate arthritis progression. Over months and years, arthritis produces chronic mild lameness, particularly after rest and exercise.

Signs: stiffness that improves with movement; lameness worse in cold weather or after long periods of rest; gradual worsening over months; bilateral involvement common.

SustainableVet.org (failure symptoms article) confirms: limping 2 years post-TPLO may result from arthritis, implant irritation, meniscal damage, or muscle atrophy.

Action required: long-term management (joint supplements, weight management, NSAIDs for flares, hydrotherapy, physiotherapy).

8. Contralateral CCL rupture

Timing: any time during or after recovery from the first TPLO.

Mechanism: the contralateral CCL, subject to the same degenerative process and bearing extra load during recovery, may rupture. The dog appears to start limping on the opposite leg.

Signs: what appears to be recovery from one side suddenly accompanied by new lameness on the opposite side; the dog may be lame on a different leg or bilateral.

Action required: veterinary evaluation; bilateral CCL disease may require staged or simultaneous bilateral TPLO.

How to assess the trajectory at home

Create a simple weekly log: note the leg-use pattern (full bearing, toe-touching, three-legged) and the dog's willingness to walk at each prescribed walk time.

Compare week 4 to week 3, week 6 to week 5. If the pattern is consistently improving, continue the protocol. If it is static or worsening, contact your vet.

For the lameness guide, see lameness after TPLO surgery in dogs. For the TPLO failure signs guide, see signs of TPLO failure in dogs and when to see a vet.

For the meniscal tear guide, see dog meniscus tear after TPLO surgery. For the infection guide, see earliest signs of TPLO infection.

Frequently asked questions

My dog was progressing well at week 4 but is limping more at week 5. What do I do?

A single week of regression after a period of progress is not necessarily pathological -- increased activity, weather changes, or an off day can cause temporary setbacks.

But if the worsening persists for 2 weeks, or is accompanied by any infection signs, contact your vet.

Monitor closely and reduce activity to the week 2 level for 24 to 48 hours to see if the leg settles.

My dog is still limping 4 months after TPLO surgery. Is this normal?

Mild residual lameness can persist to 4 months, particularly in older dogs or those with significant muscle atrophy.

However, lameness at 4 months that is not showing week-over-week improvement warrants a veterinary assessment.

A radiograph will confirm bone healing status; physical examination will assess muscle mass and stifle range of motion.

My dog is limping on the opposite leg during TPLO recovery. What does that mean?

This raises concern for contralateral CCL disease. The opposite leg is bearing extra load during recovery and may have already been compromised.

A new limp on the opposite leg during recovery warrants veterinary evaluation, including assessment and radiographs of the contralateral stifle.

Can physiotherapy reduce long-term limping?

Yes, significantly. Rebuilding the atrophied quadriceps and hip extensor muscles through controlled hydrotherapy, cavaletti exercises, and progressive strength work reduces the compensatory gait patterns that produce chronic post-TPLO lameness.

Weight management is equally important -- every additional kilogram of body weight increases stifle load.

When is limping after TPLO an emergency?

Sudden complete non-weight bearing (holding the leg entirely off the ground) after a period of normal improvement is an emergency call. Same-day emergency veterinary contact is appropriate for this presentation.

Gradual worsening that does not resolve within 24 to 48 hours is a next-day call.

Resources

• SustainableVet. Common Causes of Limping in Dogs Post-TPLO Surgery. sustainablevet.org
• Animal Outpatient Surgery. What Are the Most Common Complications of TPLO Surgery in Dogs? animaloutpatientsurgery.com
• SustainableVet. Lameness After TPLO Surgery in Dogs. sustainablevet.org
• Laveen Vet Center. Dog Limping 1 Year After TPLO Surgery. laveenvetcenter.com

It is common to notice changes in a dog's urination pattern in the first 24 to 48 hours after TPLO surgery.

Most of these changes are temporary and related to the effects of anesthesia, pain medications, and reduced mobility.

However, not urinating at all for more than 12 to 24 hours is a clinical concern that requires prompt veterinary contact.

Quick answer: Reduced urination in the first 12 to 24 hours after TPLO is usually caused by anesthesia effects, opioid medications, pain, or stress. Contact your vet immediately if your dog has not urinated within 12 hours post-surgery, or if you observe straining, vocalization, or abdominal distension.

Key takeaways

• Reduced urination in the first 12 to 24 hours is normal: anesthesia suppresses bladder awareness and opioids reduce the sensation of fullness
• Contact your vet if no urination occurs within 12 hours post-surgery: this is the critical threshold, per published veterinary guidance do not wait
• Straining, vocalizing, or abdominal swelling requires same-day veterinary evaluation: these signs suggest urinary retention requiring catheterization
• Opioid pain medications are the most common pharmacological cause: they reduce bladder filling sensation and sphincter tone in some dogs
• Surgical catheterization during the procedure may temporarily affect urination for 12 to 24 hours after catheter removal
• Increased water intake without urination is particularly concerning: it suggests the dog is producing urine but cannot eliminate it a potential retention emergency

Why dogs may not urinate normally after TPLO

Anesthesia effects

General anesthesia suppresses the entire nervous system, including the neural pathways that signal bladder fullness and initiate voiding.

As anesthetic agents clear over the first 12 to 24 hours, normal bladder signaling gradually returns.

Most dogs produce less urine during anesthesia because of reduced blood pressure and fluid redistribution.

When fluid therapy resumes and hydration normalizes after surgery, urine production increases but the dog must also have recovered enough neurological function to void normally.

Opioid pain medications

Opioid analgesics (hydromorphone, morphine, buprenorphine) prescribed after TPLO affect urination in two main ways.

They reduce the perception of bladder fullness, so the dog does not signal readiness to urinate as promptly as usual.

In some dogs they also increase urethral sphincter tone, making voiding more difficult.

JustAnswer veterinary consultation confirms: opioids can cause urinary retention by relaxing or altering bladder muscles, making it hard for the dog to pee.

This effect is temporary and typically resolves as opioid dosing decreases over the first 48 to 72 hours.

Pain and reluctance to posture

Urination requires the dog to posture squatting or lifting a leg both of which require hindlimb use and core stability that are painful in the first days after TPLO.

A dog that finds posturing too painful may suppress the urge to urinate or produce only small amounts.

Providing a non-slip surface, a low slung outdoor space (not steps or slopes), and supporting the dog with a belly sling during outdoor trips reduces posturing pain and encourages normal urination.

Surgical catheterization

A urinary catheter is often placed during TPLO surgery to drain the bladder, keep the surgical field dry, and prevent accidents during the procedure.

After catheter removal, some dogs take 12 to 24 hours to resume normal voiding patterns as the urethra recovers from catheter placement and the bladder regains normal tone.

Stress and unfamiliar environment

Dogs in pain, in an unfamiliar post-surgical environment, and wearing an E-collar may suppress urination due to stress.

Stress-related urinary suppression is temporary and usually resolves as the dog settles into the home recovery environment.

Normal urination expectations after TPLO

Most dogs urinate at least once within 6 to 12 hours of returning home from surgery. By 24 hours, most dogs have urinated multiple times.

The SustainableVet.org dog-not-peeing guide confirms: if your dog does not pee within 24 hours post-surgery, contact your veterinarian immediately to rule out complications.

The published veterinary guidance for emergency contact is: no urination within 12 hours post-surgery contact your vet.

Signs that require immediate veterinary contact

Contact your veterinarian same-day or go to an emergency clinic if you observe:

No urination at all for 12 or more hours after surgery: this is the key threshold do not wait to see if it resolves

Straining or crying during urination attempts: the dog is trying to urinate but cannot produce a stream classic urinary retention sign

Abdominal distension: the belly feels full or tense; this suggests a distended bladder (urinary retention emergency)

Drinking water but producing no urine: urine is being produced but cannot be eliminated urgent

Vomiting or lethargy alongside no urination: systemic signs accompanying urinary retention indicate a more serious emergency

Urinary retention: what happens and how it is treated

Urinary retention means the bladder cannot empty. The bladder fills progressively and becomes painful, distended, and eventually at risk of rupture if unrelieved. Prolonged retention also causes back-pressure on the kidneys.

Treatment depends on the cause:

• Catheterization: gentle placement of a urinary catheter to drain the bladder provides immediate relief and allows the bladder to recover normal tone
• Pain management adjustment: if opioid-induced retention is suspected, the analgesic protocol may be modified
• Bethanechol: a parasympathomimetic drug that stimulates bladder contraction; sometimes used in dogs with neurogenic urinary retention
• Urinalysis and culture: if infection is suspected alongside retention

Home care to encourage urination

• Scheduled outdoor trips every 2 to 4 hours for the first 24 to 48 hours
• Non-slip surface outdoors pain and weakness increase slipping risk
• Gentle belly-sling support to reduce posturing pain (fold a large towel under the belly and lift slightly)
• Quiet, calm outdoor environment stressed dogs suppress urination
• Adequate pain control contact your vet if your dog is vocalizing or reluctant to move; these are signs pain medication is insufficient
• Monitor and record each urination: time, approximate volume, any straining or discomfort

For the related incontinence guide (opposite problem), see dog incontinence after TPLO surgery: causes and care. For the post-surgical pain guide, see dog whining after TPLO surgery: causes and care.

For the full recovery guide, see what to expect after TPLO surgery in dogs. For the monitoring guide during early recovery, see post-operative care mistakes increasing TPLO infection risk.

Frequently asked questions

How long after TPLO surgery should my dog urinate?

Most dogs urinate within 6 to 12 hours of returning home from surgery. Contact your veterinarian if no urination has occurred within 12 hours.

Do not wait for the 24-hour mark if the dog is straining, vocalizing, or appears uncomfortable.

My dog is drinking water but not peeing at all. Is this an emergency?

Yes. A dog that is drinking and producing urine but cannot eliminate it (retention) needs same-day veterinary evaluation. A distended bladder is painful and can rupture.

Do not manage this at home contact your vet immediately.

Can opioid pain medications cause urinary retention?

Yes. Opioids are a recognized cause of urinary retention in both humans and dogs.

If your dog was urinating normally before surgery and stops after receiving opioid medications, this is likely a contributing factor.

Contact your vet the analgesic protocol may be modified without eliminating pain management.

What does a catheter placement during surgery do to urination afterward?

Urinary catheters are placed during TPLO to drain the bladder and keep the surgical field dry.

After catheter removal, some dogs take 12 to 24 hours to resume normal voiding as the urethra recovers.

This is expected and not a cause for alarm, as long as the dog urinates within the normal timeframe.

Is it safe to give my dog extra water if they're not peeing?

Normal hydration is essential and should be maintained. Do not restrict water.

However, if the dog is drinking normally and still not producing urine, this increases the urgency of veterinary contact rather than reducing it.

Resources

• VCA Animal Hospitals. Tibial Plateau Leveling Osteotomy (TPLO) in Dogs. vcahospitals.com
• TPLO Info. Recovery FAQs. tploinfo.com
• PetMD. Urinary Retention in Dogs. petmd.com
• Midwest Veterinary Specialists. Post-Operative Care Following TPLO. midwestveterinaryspecialists.com

High-quality radiographs are the foundation of TPLO planning and post-operative assessment. The tibial plateau angle (TPA) measurement that determines plate size, osteotomy arc, and rotation amount depends entirely on image quality.

A poorly positioned radiograph produces inaccurate TPA measurements, which can lead to undercorrection, overcorrection, or incorrect implant selection.

Understanding what makes a TPLO radiograph diagnostically reliable is essential for any veterinary professional involved in TPLO cases.

Quick answer: A diagnostic TPLO lateral radiograph requires: stifle and hock at approximately 90 degrees; tibia and fibula superimposed throughout; femoral condyles superimposed; the entire tibia visible; and the beam centered over the stifle. Femoral condyle non-superimposition is the most common cause of TPA measurement error.

Key takeaways

• Limb positioning is the single most important variable for TPA accuracy: limb positioning affects the appearance of anatomic landmarks used for TPA determination
• The femoral condyles must be superimposed on the lateral view: MDPI research confirms 3 mm non-superimposition produces 90.6% of measurements within 1 degree of true TPA; error increases substantially beyond 3 mm
• The stifle and hock should both be at approximately 90 degrees for the lateral view: this is required for accurate tibial plateau angle measurement
• Sedation is recommended: a sedated dog allows accurate limb placement without motion artifact; an unsedated dog in pain cannot maintain the required positioning
• The TPA averages 23 to 29 degrees in most dogs: some small breeds average higher; dogs with TPA over 30 degrees may be poor candidates for extracapsular repair or TTA
• Post-operative TPA target is 5 to 6.5 degrees: achieving this angle eliminates cranial tibial thrust; post-operative radiographs confirm whether the target was achieved

Why radiograph quality matters for TPLO

TPLO planning is based entirely on the pre-operative lateral stifle radiograph. From this image, the surgeon:

• Measures the TPA (tibial plateau angle)
• Selects the appropriate osteotomy saw blade radius
• Plans the rotation amount needed to achieve the target post-operative TPA (5 to 6.5 degrees)
• Selects the implant size (plate and screw dimensions)

A 2-degree error in TPA measurement from a poorly positioned radiograph can result in a plate one size too small or large, or an osteotomy rotation that undercorrects or overcorrects the joint.

Today's Veterinary Practice confirms: a well-positioned lateral stifle radiograph is essential for accurate diagnostic interpretation and TPA measurement; correct tibial alignment is most important for TPA measurement.

The lateral (mediolateral) projection

This is the critical image for TPA measurement.

Patient positioning

Body position: the dog is placed in lateral recumbency with the limb of interest (affected stifle) closest to the table. The limb is extended slightly away from the body.

Stifle angle: the stifle is positioned at approximately 90 degrees of flexion.

Hock angle: the hock (tarsus) is positioned at approximately 90 degrees of flexion.

Cave Vet Specialists confirms: ensure the stifle and hock are collimated into the area of interest; keep the leg in a natural position; place an appropriate-sized plate under the limb.

Femoral condyles: both femoral hemicondyles should be precisely superimposed. This is the most technically demanding aspect of lateral stifle radiography. To achieve superimposition, the opposite limb is elevated with foam wedges or a triangular positioning aid to allow the limb of interest to lie flat and parallel to the table.

Cave Vet Specialists confirms: place the non-interest limb onto wedges to tilt the limb of interest centrally; place a triangular wedge or sandbag on the opposite side.

Tibia-fibula superimposition: the tibia and fibula should be superimposed throughout their full length. If the tibia and fibula are not superimposed, the tibia is rotated relative to the plate -- and this same rotation is captured in the TPA measurement.

What to include

The radiograph must include the entire tibia from the tibial plateau (top) to at least the distal metaphysis (ideally the entire bone).

Today's Veterinary Practice confirms: the x-ray beam should be centered over the stifle joint with collimation to include the entire tibia.

The most common positioning errors

Femoral condyle non-superimposition: the most frequent and most impactful error. Caused by the hindquarters tilting, the contralateral limb not elevated sufficiently, or the dog being unsedated and shifting position.

The MDPI Animals research quantified the impact: 3 mm of non-superimposition produces about 1 degree of TPA error; errors increase substantially beyond 3 mm.

Tibial rotation: the tibia is internally or externally rotated relative to the true mediolateral plane. This occurs when the hock is not held in a natural position. Rotation changes the apparent slope of the tibial plateau and produces a falsely high or low TPA.

Today's Veterinary Practice confirms: the tibia can easily be rotated with CCL injury even when the femur appears straight.

Incomplete tibia: if the distal tibia is cut off by collimation, the surgeon cannot assess the full tibial axis -- which is required for TPA measurement.

The caudocranial (CrCd or AP) projection

The caudocranial view assesses limb alignment, varus and valgus deformity, and tibial torsion. It is a standard part of the pre-operative TPLO radiograph set.

Patient positioning

The dog is placed in sternal recumbency or dorsal recumbency with the affected limb extended caudally (toward the x-ray plate). The stifle and hock should be visible.

Rita Leibinger confirms: the AP projection must have the stifle and tarsus included for the attending surgeon to assess limb alignment.

DVM360 confirms: on the caudocranial view, the medial margin of the tuber calcis should align with the center of the distal tibia, confirming the absence of tibial torsion.

Calibration for surgical planning

When radiographs will be used for surgical planning (plate size selection), a calibration marker must be placed at the same level as the stifle joint.

This allows the surgeon to scale the digital image to real-world measurements.

Rita Leibinger confirms: image calibration does not alter TPA measurement (the angle is size-independent), but it enables radiographs to be used for surgical plate-size planning.

Post-operative radiographs

After TPLO, radiographs are taken:

• Immediately post-surgery: to confirm osteotomy position, plate position, screw placement, and achieved post-operative TPA
• At 6 to 8 weeks: to assess early bone healing and callus formation
• At 12 weeks: to confirm bone union before lifting activity restrictions

What a good post-operative radiograph shows

• Post-operative TPA of approximately 5 to 6.5 degrees
• No screws violating the joint space
• Plate in correct medial position on the tibia
• Osteotomy gap that is progressively narrowing on follow-up films (callus formation)

Warning signs on post-operative radiographs

• Screw tip in the joint space (requires removal of that screw)
• Plate migration from original position
• Peri-implant radiolucent halos (suggests implant loosening or infection)
• Osteotomy gap not narrowing by 8 weeks (suggests delayed union or infection)

For the TPA measurement guide, see what causes TPLO surgery in dogs. For post-operative complications, see 15 common complications after TPLO surgery.

For the plate infection guide, see TPLO plate infection signs and treatment. For bone healing information, see TPLO bone healing time in dogs.

Frequently asked questions

Does the dog need to be sedated for TPLO radiographs?

Sedation is strongly recommended and preferred. An unsedated dog -- particularly one in pain from CCL disease -- cannot maintain the precise positioning required for accurate TPA measurement.

Even minor position changes between preparation and exposure produce significant error. Sedation allows the technician to position the limb correctly and hold it in place without the dog shifting.

Why does the hock position matter for the lateral view?

The hock angle affects the position of the tibia relative to the table and the imaging plate.

When the hock deviates from approximately 90 degrees, the tibia is either elevated or depressed at the distal end, which changes the apparent angle of the tibial plateau.

This error is captured in the TPA measurement.

What is a normal TPA range and when should TPLO be recommended?

Today's Veterinary Practice confirms the average TPA in most dogs is 23 to 29 degrees. Some small breeds have higher averages.

Dogs with TPA greater than 30 degrees may be poor candidates for extracapsular repair or TTA.

TPLO is appropriate for dogs of all TPA values -- the procedure specifically corrects whatever TPA angle the dog presents with.

Can the same radiograph be used for both diagnosis and surgical planning?

Yes, if it is of adequate quality and includes a calibration marker.

Diagnostic-only radiographs taken without a calibration marker can confirm CCL disease and measure TPA, but cannot be used for plate-size surgical planning.

Including a calibration marker at the time of acquisition allows a single radiograph to serve both purposes.

What happens if the TPA is measured incorrectly pre-operatively?

If the pre-operative TPA is underestimated, the surgeon may under-rotate the osteotomy and fail to reach the target 5 to 6.5 degree post-operative TPA.

This results in residual cranial tibial thrust and potentially ongoing instability. If overestimated, overcorrection is possible.

This underscores why positioning accuracy at the time of radiography is critical -- errors propagate through the entire surgical plan.

Resources

• Cave Vet Specialists. Tips for TPLO Radiographs. cave-vet-specialists.co.uk
• Today's Veterinary Practice. Cruciate Disease: How and Why to Measure Tibial Plateau Angle. todaysveterinarypractice.com
• MDPI Animals. The Effect of Femur Positioning on Measurement of Tibial Plateau Angle. ncbi.nlm.nih.gov
• Rita Leibinger. TPLO Surgical Technique. leibinger.vet

After TPLO surgery, one of the most important questions owners and rehabilitation teams ask is: how much weight should my dog be putting on the operated leg right now?

The Arthrex TPLO weight chart provides a structured, week-by-week answer to that question, giving both surgeons and owners a shared reference point for tracking recovery progress.

Quick answer: The Arthrex TPLO weight chart tracks the percentage of body weight a dog bears on the operated leg at each recovery stage — from 0 to 10% in the first weeks to 100% by 8 to 12 weeks post-surgery.

Key takeaways

• The weight chart tracks weight-bearing percentage at each stage, from 0 to 10% in weeks 1 to 2 to 100% by weeks 8 to 12
• It is a rehabilitation monitoring tool, not a surgical planning tool: the rotation chart governs intraoperative correction; this tracks recovery
• Progression must be gradual: advancing too fast risks implant failure; too slow leads to atrophy and stiffness
• The chart integrates with clinical examination: 8-week radiographs, gait assessment, and muscle mass evaluation are considered alongside chart milestones
• Individual dogs vary: the chart provides population-level benchmarks; your surgeon's instructions take precedence
• The chart is used alongside the plate size and rotation charts: together they form the Arthrex TPLO system framework

What the weight chart is and what it is not

The Arthrex TPLO weight chart is a post-operative rehabilitation tool.

It shows recommended weight-bearing percentages at specific time points after surgery a reference guide that helps veterinarians, rehabilitation therapists, and owners track whether a dog's recovery is progressing appropriately.

It is not the same as the rotation chart (which guides intraoperative tibial rotation) or the plate size chart (which guides implant selection before surgery).

These three charts together form the Arthrex TPLO planning and monitoring system.

For the rotation chart guide, see Arthrex TPLO rotation chart explained. For the plate overview, see Arthrex TPLO plate overview and use.

Understanding the weight-bearing percentages

The chart uses percentage of body weight as its unit of measurement.

This is a more useful measure than time alone because it relates directly to the mechanical load placed on the healing osteotomy and implant.

0 to 10% weight-bearing (weeks 1 to 2): toe-touching and minimal contact only. The dog is not actively loading the leg during this phase. Bathroom trips on leash are permitted, but no sustained weight-bearing.

10 to 30% (weeks 2 to 4): the dog begins placing meaningful weight on the leg during slow leash walks. This corresponds to the short 5 to 10 minute leash walks prescribed at this stage. The healing osteotomy is starting to consolidate but is not yet ready for full load.

30 to 60% (weeks 4 to 8): progressive loading during longer walks, sit-to-stand exercises, and early rehabilitation activities. Most dogs are visibly improving in gait symmetry during this phase.

60 to 100% (weeks 8 to 12): full weight-bearing is approached and typically achieved after the radiographic recheck at week 8 confirms adequate osteotomy healing. Activity levels increase under veterinary guidance.

How to use the chart in practice

As a clinical benchmark

Surgeons use the weight chart to assess whether a dog is progressing as expected at each recheck visit.

A dog that is well below the expected weight-bearing percentage for their stage may have inadequate pain control, implant complications, or infection.

A dog exceeding the expected percentage may be at risk of mechanical overload if the bone has not yet consolidated enough to tolerate the load.

As an owner reference

Owners are not expected to measure exact weight-bearing percentages at home this requires force plate analysis or pressure-sensitive walkway equipment.

The chart provides a conceptual framework: early recovery shows only toe-touching; by weeks 4 to 6, the dog places meaningful weight during walks; by weeks 10 to 12, gait symmetry improves steadily.

What affects weight-bearing progress

Bone healing rate: younger dogs and smaller breeds typically consolidate the osteotomy faster than older or giant breed dogs.

Pain control: inadequate analgesia is the most common cause of delayed weight-bearing. A dog in pain will protect the operated leg regardless of how well the surgery went. Contact your surgeon if your dog is significantly below expected weight-bearing benchmarks.

Muscle atrophy: dogs that enter surgery with significant muscle atrophy from prolonged pre-surgical lameness progress more slowly and benefit most from structured rehabilitation.

Body weight: heavier dogs place more absolute load on the healing osteotomy at any given percentage. This is one reason weight management is emphasized throughout the TPLO recovery period.

Rehabilitation: dogs receiving structured rehabilitation (PROM, sit-to-stand, hydrotherapy) consistently achieve better weight-bearing progression than those managed with rest alone.

When the chart says one thing and your dog does another

The weight chart represents population-level expectations. Individual dogs routinely deviate from the expected timeline for reasons that are often identifiable and manageable.

If your dog is significantly under-progressing: contact your surgeon to rule out infection, implant problems, or inadequate pain management before assuming slow healing.

If your dog appears to be weight-bearing well ahead of schedule: this does not mean the osteotomy is healed faster than expected.

Radiographic confirmation at week 8 is still required regardless of how the dog looks clinically. Apparent early function does not mean the bone has consolidated enough to withstand full unrestricted activity.

For the full weight-bearing recovery timeline guide, see how soon can a dog walk after TPLO surgery.

For the rotation chart that is used alongside the weight chart in the Arthrex system, see Arthrex TPLO rotation chart explained.

For the plate size chart used in conjunction with both, see TPLO plate size chart explained.

Frequently asked questions

Is the Arthrex TPLO weight chart the same as a standard recovery timeline?

Not exactly. A recovery timeline tells you what activities to do and avoid at each stage.

The weight chart specifically tracks how much weight the dog is placing on the operated leg at each stage, expressed as a percentage of body weight.

The two are related but provide different information.

Can I measure my dog's weight-bearing at home?

Not precisely. Force plate and pressure-sensitive walkway systems that measure actual weight distribution require specialist veterinary equipment.

At home, you can observe whether the dog is toe-touching, placing the foot flat, and walking with increasing symmetry which approximates the chart's progression categories without exact percentages.

What if my dog refuses to use the leg at all two weeks after TPLO?

Non-weight-bearing at two weeks is a warning sign. TPLO Austin confirms that if your pet is not bearing weight within two weeks of surgery, contact your veterinarian.

The most common causes are inadequate pain control, infection, or implant positioning concerns all of which are addressable if caught early.

Do all TPLO surgeons use the Arthrex weight chart?

No. The Arthrex system is one of the two major TPLO implant systems in the US (alongside Synthes). Surgeons using Synthes implants use Synthes-specific planning tools.

Some surgeons use individualized rehabilitation protocols rather than system-specific charts. The underlying recovery milestones are similar regardless of which chart or system is used.

What happens at the 8-week recheck in terms of weight-bearing?

At the 8-week recheck, radiographs assess osteotomy healing. If healing is adequate, the surgeon approves increased activity typically 20 to 30 minute leash walks and the beginning of return-to-normal activity.

The weight chart at this point expects the dog to be approaching or achieving 100% weight-bearing on the operated leg.

Resources

• Arthrex Veterinary. TPLO Surgical Technique. arthrex.com
• VCA Animal Hospitals. Tibial Plateau Leveling Osteotomy (TPLO) in Dogs. vcahospitals.com
• TPLO Austin. Step 6: TPLO Surgery Recovery. tploaustin.com
• ACVS. Cranial Cruciate Ligament Disease. acvs.org