Investigation of naturally occurring osteoarthritis in the metacarpophalangeal joints of wild horses : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science at Massey University
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Date
1997
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Massey University
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Abstract
The purpose of this study was to assess the site, prevalence and characteristics of lesions affecting the proximodorsal aspect of the first phalanx (P1) in the forelimbs of wild
horses.
An investigation was made of the metacarpophalangeal joints of 22 wild New
Zealand horses with a mean age of 7.36 + 3.27 years (range 2 - 14 years). The articular
surfaces of the metacarpophalangeal joints were stained with Indian ink and macroscopic
lesions on the medial and lateral eminences of P 1 were graded. Radiographs were taken
of 2mm thick sagittal bone slabs sawn from both the lateral and medial eminences of
proximodorsal first phalanx. The subchondral bone mineral density for five regions on
the proximo-dorsal aspect of each bone slab was determined using a Norland XR-26 bone
densitometer. Histological sections of the bone slabs were then prepared and the articular cartilage lesions on the proximo-dorsal aspect of Pl were assessed using both subjective and objective scoring methods.
Subjective assessment of cabinet radiographs showed subchondral bone sclerosis
to be greater in those horses with severe articular cartilage damage. The subchondral bone mineral density also increased with age and with increasing severity of lesions in the overlying articular cartilage. Ossicles with a distinct trabecular bone pattern were identified at the proximo-dorsal margin of P 1 in eight specimens from 5 horses. The macroscopic and histological articular cartilage scores increased significantly with age and the lesions were more severe on the medial compared with the lateral eminence of Pl.
The study demonstrated cartilage changes, wear lines and subchondral sclerosis,
consistent with osteoarthritis in the metacarpophalangeal joint of wild horses. The
severity of the changes increased with age. There was a significant relationship between subchondral bone sclerosis and overlying cartilage changes in the proximo-dorsal aspect of Pl. The observations represent an age-related osteoarthritic process that may be present in all horses.
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Keywords
Osteoarthritis in horses, Wild horses, Metacarpophalangeal joints, Arthritis in animals