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June 2007

Horse, femoropatellar joint, osteochondrosis dissecans of lateral trochlea

Detailed information.

Animal: Horse, 5 months, thoroughbred, male.

Organ: Joint.

Autopsy findings: The left knee joint was swollen. The joint cavity contained an abundant amount of serohemorrhagic fluid. The cartilage of the lateral trochlea of the distal left femur was irregularly thickened from the interface with the condyle and 2.5 cm in proximal direction. On cut section, the lesion appeared to consist of thickened, partly hyperaemic cartilage, not sharply demarcated from the surrounding subchondral bone. In the central part of the lesion, a fissure in the cartilage penetrated from the abaxial margin of the joint in an axioproximal direction. A projection of irregular cartilage penetrated 3 cm from the interface between bone and cartilage into the subchondral bone and ended in a cystic lesion with a diameter of 0.7 cm. On histological examination the lesion consisted of thickened cartilage surrounded by granulation tissue. Deep to the granulation tissue, there were islands of fibrocartilaginous tissue, the bone marrow was partly filled with connective tissue and the bone trabeculae were thinner and more delicate than in the surrounding areas. The central part of the thickened cartilage contained several necrotic cartilage canals, traversing the tissue from the subchondral bone. These canals were surrounded by areas of necrotic cartilage.

Diagnosis: Osteochondrosis dissecans, ischemic necrosis of epiphyseal growth cartilage

Necropsy performed by : Mona Aleksandersen and Bjørnar Ytrehus

Photo by: Bjørnar Ytrehus