Hereditary and clinical characteristics of lateral luxation of the superficial digital flexor tendon in Shetland sheepdogs.

A study was conducted to define the mode of inheritance of lateral luxation of the superficial digital flexor (SDF) tendon in different lines of Shetland sheepdogs by examination of pedigree data. This pedigree analysis included affected and unaffected dams, sires, and offspring; common clinical signs; and age at onset. The clinical, histopathologic, and radiographic features of the disease were also studied. Of the 14 offspring from five matings of an affected sire to unrelated affected females, 100% were affected with lateral luxation of the SDF tendon. Of the 59 offspring from the same affected sire to unrelated, unaffected females, 44% were affected. The mating between normal parents produced 61% unaffected and 39% affected offspring. Application of the phenotypic findings in this study to a Mendelian genetic model of inheritance suggests that lateral luxation of the superficial digital tendon in Shetland sheepdogs is inherited as a simple autosomal recessive trait.