Pathological and radiological investigations on osteochondrosis in pigs, associated with leg weakness.

Two-hundred and seventy-eight Danish Landrace boars were examined radiologically and pathologically for osteochondrosis and other joint lesions on the left legs at slaughter (95 kg). The joint changes were scored on a scale from 1 (normal) to 5 (very severe changes/osteochondritis dissecans). The correlations between radiological and pathological scores were highly significant in the humeral condyles (r = 0.66, P < 0.001), the distal ulna growth plate (r = 0.51, P < 0.001), the femoral condyles (r = 0.33, P < 0.001) and hock (distal tibia (r = 0.17, P < 0.01) and the medial trochlear ridge of the talus (r = 0.17, P < 0.01), indicating that radiographical examination is a useful method for diagnosing osteochondrosis in live pigs. Thickening of cartilage was strongly associated with subchondrial lesions in the three predilection sites: the humeral condyle, the femoral condyles and the distal ulna growth plate. Osteochondritis dissecans (OCD) in the humeral condyles was significantly associated with subchondral lesions (OR = 1.86; P < 0.001), but not with cartilage thickness when analysed simultaneously. There were no associations between lesions in the distal ulna growth plate, the humeral condyles, the femoral condyles or the anconeal process. There was no significant correlation between OCD in the humeral condyles and the anconeal process. Osteochondrosis could therefore not be stated to be a generalized disorder. Regression coefficients between joint changes and leg weakness symptoms judged before slaughter were very small and showed no clear trends. OCD in the humeral condyles was, however, significantly associated with 'legs turned out on fore (OR = 2.48; P < 0.001) and hind (OR = 1.62; P < 0.05) legs', and OCD in the anconeal process with 'stiff movement in front' (OR = 2.01; P < 0.05). Osteochondrosis is thus comparable with a threshold trait, where the threshold is the development of an OCD in an osteochondrosis injured joint.