Epsilon Open Archive

Abstract

Osteochondral lesions in the joints of the distal tarsal
region of young Icelandic horses provide a natural model
for the early stages of osteoarthritis (OA) in low-motion
joints. We describe and characterise mineralised and
non-mineralised osteochondral lesions in left distal tarsal
region joint specimens from twenty-two 30 ±1 month-old
Icelandic horses. Combinations of confocal scanning light
microscopy, backscattered electron scanning electron
microscopy (including, importantly, iodine staining) and
three-dimensional microcomputed tomography were used
on specimens obtained with guidance from clinical imaging.
Lesion-types were described and classified into groups
according to morphological features. Their locations in
the hyaline articular cartilage (HAC), articular calcified
cartilage (ACC), subchondral bone (SCB) and the joint
margin tissues were identified and their frequency in the
joints recorded. Associations and correlations between
lesion-types were investigated for centrodistal joints only.
In centrodistal joints the lesion-types HAC chondrocyte
loss, HAC fibrillation, HAC central chondrocyte clusters,
ACC arrest and ACC advance had significant associations
and strong correlations. These lesion-types had moderate
to high frequency in centrodistal joints but low frequencies
in tarsometatarsal and talocalcaneal-centroquartal joints.
Joint margin lesion-types had no significant associations
with other lesion-types in the centrodistal joints but high
frequency in both the centrodistal and tarsometatarsal
joints. The frequency of SCB lesion-types in all joints
was low. Hypermineralised infill phase lesion-types were
detected. Our results emphasise close associations between
HAC and ACC lesions in equine centrodistal joints and the
importance of ACC lesions in the development of OA in
low-motion compression-loaded equine joints.