Periarticular ossification at the elbow joint and meniscal ossification in the stifle joint of pigs--occurrence, pathomorphology, breed differences and correlations with osteochondrosis, leg weakness and production parameters.

The occurrence, pathomorphology, and possibly impact of periarticular ossification at the elbow joint and meniscal ossification in the stifle joint are described. A total of 4029 boars of the Landrace and Yorkshire breeds were performance tested and examined radiologically. Periarticular ossification at the elbow joint was found in radiographs at a prevalence of 0.9%. Meniscal ossification was seen as single or multiple foci at the cranial aspect of the joint at a prevalence of 2.6%, and had a bilateral occurrence in 20%. Significant breed differences (P < 0.001) were found for both joint processes. The meniscal ossifications were associated with hindlegs turned out (abduction) (P < 0.001) and stiff locomotion in the rear (P < 0.001), and were negatively (adversely) associated with growth rate (P < 0.01). The periarticular osseous foci were seen as focal firm swellings at the craniomedial aspect of the elbow joint. The meniscal ossifications were observed as single or multiple small, smooth, firm, and irregular swellings in the cranial horn of only the lateral meniscus. The histomorphology of both types of ossifications was similar. Centrally, they were made up by osseous trabeculae. The trabeculae might contain clusters of chondrocytes. Between the trabeculae, which were lined with flat osteoblasts, adipocytes were present. The osseous centre was encircled by mineralized cartilage that blended into more or less fibrous cartilage. However, towards the joint cavity the meniscal ossifications were covered by hyaline cartilage.