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Featured Article | Research Article | 05 Jun 2026

Radiographic evaluation of patellofemoral proportional mismatch in small-breed dogs with medial patellar luxation: Implications for stifle joint morphology and surgical planning

Ekkapol Akaraphutiporn1, Khemupsorn Kaewmahing1, Pichamon Chunhasewee1, Sansinee Fuengsil1, Tawanrat Chaiyaphan1, and Chalika Wangdee1,2 Show more
VETERINARY WORLD | Article No. 3 | pg no. 2293-2303 | Vol. 19, Issue 6 | DOI: 10.14202/vetworld.2026.2293-2303
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ABSTRACT

                      
Background and Aim: Medial patellar luxation (MPL) is a common orthopedic disorder in small-breed dogs and is closely associated with abnormalities of the patellofemoral joint. Although trochlear dysplasia is widely recognized, the proportional relationship between the patella and distal femur remains insufficiently explored. This study aimed to perform a comprehensive radiographic morphometric evaluation of patellofemoral structures to identify anatomical factors associated with MPL and to assess their relevance for surgical planning. 
Materials and Methods: A total of 69 stifles from 46 small-breed dogs were evaluated and categorized into control, MPL grade II, and MPL grade III groups. Standardized ventrodorsal, mediolateral, and skyline radiographic projections were used to measure patellar width (PW), patellar height (PH), patellar length (PL), femoral width (FW), femoral condyle size (FC), trochlear width (TW), trochlear depth (TD), trochlear length (TL), and sulcus angle (SA). Morphometric ratios, including PW/TW, PH/TD, PL/TL, PW/FW, and PH/FC, were calculated. Statistical analysis was conducted using one-way analysis of variance with Tukey’s post hoc test (p < 0.05). 
Results: Patellar dimensions (PW, PH, PL) did not differ significantly among groups, indicating that patellar morphology alone was not associated with MPL severity. In contrast, distal femoral parameters showed significant alterations. The MPL grade III group exhibited significantly reduced TD compared with grade II, and increased SA compared with both control and grade II groups, reflecting progressive trochlear flattening. The PH/TD ratio was significantly higher in the MPL grade III group, suggesting a proportional mismatch between patellar size and trochlear groove depth. Other ratios did not show significant differences, although PL/TL demonstrated an increasing trend in affected stifles. 
Conclusion: MPL in small-breed dogs is primarily associated with distal femoral morphological abnormalities rather than absolute patellar size. Trochlear shallowness and increased SA, along with an elevated PH/TD ratio, highlight the importance of patellofemoral proportional mismatch in disease pathogenesis. These findings emphasize the need for comprehensive morphometric evaluation during preoperative planning to optimize surgical outcomes. 
                      
Keywords: anatomical measurement, medial patellar luxation, morphometric analysis, patellofemoral mismatch, radiographic evaluation, skyline radiograph, small-breed dogs, trochlear dysplasia.