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Patellar Tendonitis After TPLO Surgery in Dogs

Patellar Tendonitis After TPLO Surgery in Dogs

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Owners

Learn about patellar tendonitis after TPLO surgery in dogs, including causes, symptoms, treatment, and recovery tips for pet owners.

By 

Sustainable Vet Group

Updated on

August 13, 2026

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

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

Patellar Tendonitis After TPLO Surgery in Dogs

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

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