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This descriptive study aimed to compare the magnetic resonance appearance of the distal interphalangeal joint articular cartilage between standing weight-bearing and non-weight-bearing conditions. Ten forefeet of live horses were scanned in a standing low-field magnetic resonance system (0.27 T). After euthanasia for reasons unrelated to the study, the non-weight-bearing isolated feet were scanned in a vertical positioning reproducing limb orientation in live horses. The same acquisition settings as during the weight-bearing examination were used. Thickness and cross-sectional area of the distal interphalangeal articular cartilage and joint space were measured on tridimensional T1-weighted gradient echo high resolution frontal and sagittal images at predetermined landmarks in both conditions and were compared using a linear mixed-effects model. Frontal images were randomized and submitted to 9 blinded readers with 3 different experience levels for identification of weight-bearing versus non-weight-bearing acquisitions based on cartilage appearance. Weight-bearing limbs had significantly thinner distal interphalangeal cartilage (p = 0.0001) than non-weight-bearing limbs. This change was greater in the distal phalanx cartilage than that of the middle phalanx. Blinded readers correctly identified 83% (range 65 to 95%) of the images as weight-bearing or non-weight-bearing acquisitions, with significantly different results observed among the different readers (p < 0.001) and groups (p < 0.001). These results indicate that distal interphalangeal articular cartilage and particularly cartilage of the distal phalanx thins when weight-bearing compared to the non-weight-bearing standing postmortem conditions and suggest that cartilage abnormalities may be more difficult to identify on weight-bearing standing magnetic resonance imaging.

Radiographic screening in young horses is an useful tool for early detection of developmental orthopedic disease (DOD), a worrying problem for owners, trainers and veterinaries. Radiographies of 700 horses (676 in Belgium, 24 in Sardinian) have been examined to study prevalences of most common pathologies (Studio I), correlation between foot conformation and presence of effusion at the distal interphalangeal joint (Studio II), usefulness of LM view in detection of DOD at the hock (Studio III). The horses were 3-4 years of age, free of lameness. DOD of osteochondral and degenerative type showed the highest prevalences and were found mostly in stifle and hock joints of the belgian group while front feet and fetlocks were more affected in the sardinian group. Effusion at the distal interphalangeal joint was positively correlated with foot conformation with low distal phalanx angle, low hoof angle, long toe and low heels, suggesting the need of proper corrective trimming of the hoof before the beginning of their training in order to prevent improper mechanical stress. In the radiographic examination of the hock, the LM view provides the largest number of radiographic signs for the diagnosis of lesions with the exception of osteochondrosis of tibial malleolus, compared with each one of the other views. Good agreement between readers of different experience demonstrated the usefulness of an evaluation grid to be available during selection of horses for reproducing purposes.