INTRA-ARTICULAR CHARACTERISTICS OF DOGS WITH MEDIAL PATELLAR LUXATION

Abstract

The study investigated the relationship of degree of patellar luxation of dogs with joint radiography, intra-articular degenerative change of the stifle with medial patellar luxation (MPL), histopathologic change, and biomarker index. Thirty-eight stifles were divided into four groups: normal stifle joints (4), grades 2 (13), 3 (12), and 4 (9) MPL. Demographic data, lameness score, and degree of patellar luxation of all dogs were assessed and recorded. Radiographs were taken to assess osteophyte formation. Synovial tissue was collected for microscopic evaluation differential cell counts, and cytokines measurement. Stifle joints with MPL were scored during surgical correction. All observed data were analyzed for correlations and differences among the normal and MPL stifle groups. There were significant differences in the lameness score between the normal and grades 3 and 4 MPL groups, the histopathologic score between normal and grade 4 MPL groups, the osteoarthritis (OA) score between normal and all grades of MPL. Correlations were found between degree of patellar luxation and the lameness, histopathologic, and synovial scores. Correlations of OA and the cartilage score were found with duration of luxation as well as age at surgery. Correlations were found between the synovial score and the lameness score, foam cell, and histopathologic score. The cartilage score was significantly correlated with number of neutrophils. In addition, correlations were found between the radiographic score and the OA and cartilage scores. In conclusion, MPL in small breed dogs can cause stifle OA. Radiographic score was correlated with cartilage score and OA score but the severity of OA was not related to the severity of PL. Only MCP-1 was found in synovial fluid but correlation of MCP-1 with other parameters was not found. The reason was that other cytokines relating to the severity of OA could not be detected in this study. MPL in small breed dogs might cause less OA than that in the large breed dogs and dogs with cranial cruciate ligament rupture. Severity of cartilage erosion and OA are related with duration of disease and age of dogs. Therefore, surgical correction should be performed as soon as possible in order to prevent further development of degenerative joint disease.