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Osteoarthritis (OA) of the low motion joints of the tarsus, commonly termed 'bone spavin', is common in horses. Whilst the aetiology of this condition is multifactorial, it has been suggested that dorsal wedging of the central tarsal bone (CTB) and third tarsal bone (TTB) may predispose to the development of this disease. The aim of this study was to investigate the relationship between tarsal bone conformation and osteoarthritis of the proximal intertarsal (PIT), distal intertarsal (DIT) and tarsometatarsal (TMT) joints. It was hypothesised that wedging of the CTB and TTB would be associated with OA in these joints. Multiplanar reconstructions based on computed tomographic (CT) images were used to measure the height of the central and third tarsal bones at their dorsal and plantar aspects in three parasagittal planes in cadaver specimens. A wedging index was calculated as the ratio between the dorsal and plantar measurements. All tarsal bones were graded for OA on CT images. There was a significant moderate negative correlation between the wedging index of the CTB and OA of the DIT (ρ = -0.45, P <0.01), TMT (ρ = -0.49, P <0.01) and PIT joints (ρ = -0.43, P <0.01). Dorsal wedging of the TTB was seen in mild and moderate grades of OA, but severe cases of OA were associated with plantar wedging. Our study suggests that wedging of the small tarsal bones is associated with OA in the associated joints and hence care should be taken in foals to prevent the development of wedging.

Original publication




Journal article


Vet J

Publication Date





94 - 98


Conformation, Equine, Osteoarthritis, Spavin, Tarsus, Animals, Cadaver, Horse Diseases, Horses, Osteoarthritis, Tarsus, Animal