The current project has a basic science and a clinical relevance part. The main project aim is to describe the blood supply to the growth cartilage of the small tarsal bones in young Icelandic Horses. Similar studies of the blood supply to long bones that ossify from three separate centers have yielded entirely new information confirming that osteochondrosis, which can lead to fragments in joints (osteochondrosis dissecans) is the result of focal failure of this blood supply. It is not known whether the blood supply to the small tarsal bones, which ossify from a single center, is organized in the same way. The relationship between blood supply and wedge-shaped bones that cause sickle hocks will be investigated. The relationship between blood supply and developmental, heritably predisposed joint inflammation/osteoarthritis or spavin, which is common in Icelandic horses, will be examined. This will yield valuable information that potentially is relevant to osteoarthritis in general.