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Patella luxation and rupture of the cranial cruciate ligament

Medial Patella Luxation (MPL) and Cranial Cruciate Ligament Rupture frequently coexist, with studies revealing that 25% of middle-aged to older dogs with MPL develop concurrent ligament rupture (Campbell, 2010).

Untreated MPL in dogs often progresses to severe grades as they age (Roush, 1993). This progression leads to skeletal deformities, joint effusion, and degenerative joint disease, contributing to Cranial Cruciate Ligament Rupture (Campbell, 2010).

Clinical Signs

Clinical signs range from mild to severe lameness, worsening with exercise.


Diagnosis involves physical examination and radiographs. Examination may reveal patella luxation, joint instability during cranial drawer movement, and fibrosis thickening on the medial aspect (medial butters). Radiographs may show joint effusion, medial butters, limb deformity, and patella luxation.


Tailored treatment, based on examination and radiographs, addresses both Cranial Cruciate Ligament Rupture and MPL.

- Cranial Cruciate Ligament Treatment: TPLO surgery corrects the ligament.


- Patella Luxation Treatment: Trochlear Wedge Resection and quadriceps mechanism realignment are employed. Quadriceps realignment corrects tibial or femoral limb deformities. Femoral correction involves osteotomy.

“Modify” TPLO

A complex procedure, "modify" TPLO corrects proximal tibial angles and shifts the tibial plateau medially to align the quadriceps. This method, more demanding, is preferred in toy breed dogs.

"Modify" TPLO vs. TPLO plus Transposition of the Tibial Crest

While some prefer a combination, "modify" TPLO is favoured due to its single osteotomy, reducing complications such as delay union, avulsion crest, or pin migrations, especially in active patients.


Campbell, A.C., Hortsman L.C., Mason D.R. et al. (2010) ' Severity of patellar luxation and frequency of concomitant cranial cruciate ligament rupture in dogs: 162 cases (2004–2007)' . JAVMA 236(8). p 887-891

Roush, J.K. (1993) 'Canine patellar luxation'. Vet Clin North Am Small Anim Pract 1993;23. p 855–868.

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