Martin Waselau, Dr med vet, MS; W. Wesley Sutter, DVM, MS, DACVS; Ronald L. Genovese, VMD; Alicia L. Bertone, DVM, PhD, DACVS Journal of the American Veterinary Medical Association May 15, 2008 Vol. 232 No. 10 Pages 1515-1520 Objective—To determine outcome of Standardbred racehorses with moderate to severe midbody suspensory ligament desmitis (MSD) treated by means of ultrasound-guided intralesional injection of a single dose of platelet-rich plasma (PRP) followed by a program of gradually increased exercise. Design—Nonrandomized clinical trial. Animals—9 Standardbred racehorses. Procedures—Following injection of PRP, horses were allowed a controlled, gradual return to exercise. Race records for the year prior to injury and for 3 consecutive years after horses returned to racing were reviewed. For comparison purposes, race records of 9 Standardbred racehorses with no history of MSD racing at the same time were also reviewed. Results—All 9 horses with MSD returned to racing after treatment; median time to return to racing was 32 weeks. All 9 horses raced at least once during the first and second years after returning to racing, but only 5 raced during the third year. When number of starts, total earnings, and earnings per start were compared between case and comparison horses, the only significant differences were number of starts during the third year after case horses returned to racing and earnings per start during the first year after case horses returned to racing, with values being significantly lower for case horses than for comparison horses. Conclusions and Clinical Relevance—Results suggested that horses with moderate to severe MSD treated by means of intralesional injection of a single dose of PRP followed by a program of gradually increased exercise had an excellent prognosis for returning to racing.