Objective- To describe of occurrence of the forelimb joint lesions in racehorses by radiographic imaging Design- Case series study Animals- 310 racehorses (Turkmen, Thoroughbred, Arabian and mixed breed) were referred to Veterinary Teaching Hospital, Ferdowsi University for soundness evaluation due to poor athletic performance during the period from 2010 to 2014. Procedures- After clinical and hematological examinations, radiographic evaluations of forelimb joints were performed in clinically suspected racehorses. Type and location of the lesions were determined radiographically. Results- Abnormal radiographic findings of the forelimb joints were described in 100 joints related to 65 horses. Of these 65 horses, 33 (50.76%) were female and 32 (49.23%) were male. The age distribution was from 24 days to 24 years old. In this study, 2-4 year old horses were major of population (80.92%). Radiologic evaluations were shown joint lesions in the carpal joints (53%), the fetlock joints (31%) and the other forelimb joints (6%). Fractures (56.45%), DJD (29.83%), OCD (9.67%) and arthritis (4.03%) were the common lesions of the affected joints, respectively. In the carpus, fractures tended to occurred at higher rates in the intermediate carpal (33.33%) and radiocarpal (31.48%) bones than distal end of radius (16.66%) and third carpal bone (16.66%). The most common articular fractures were occurred in antebrachiocarpal joint (59.09%). The fractures in middle and carpometacarpal joints were 38.63% and 2.27%, respectively. Chip fractures were the most type of fracture (76.78%) in the carpal joints. In fetlock joint, occurrence of chip fractures and OCD were 91.66% and incomplete fractures were 8.33%. 54.16% and 45.83% of chip fractures and OCD were involved 3rd metacarpal bone and first phalanx, respectively. Conclusion and Clinical Relevance- Whereas the prevalence and distribution of the forelimb joint lesions differ among breeds, this study reported the occurrence, type and location of these lesions in the racehorses were referred to Veterinary Teaching Hospital, Ferdowsi University of Mashhad. Based on current study, radiography is a major modality for precise diagnosis of the joint lesions and it should be done for any clinically suspected joints.

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