Chris D. Bell, DVM; Rick D. Howard, DVM, PhD, DACVS; D. Scott Taylor, DVM, DACVS; Ed D. Voss, DVM, DACVIM; Natasha M. Werpy, DVM, DACVR Journal of the American Veterinary Medical Association April 1, 2009 234 7 920-925 Objective—To determine clinical outcome following intrathecal injection of the podotrochlear (navicular) bursa for signs of foot pain in horses evaluated via magnetic resonance imaging (MRI) and evaluate efficacy of corticosteroids administered with or without hyaluronate. Design—Retrospective case series. Animals—23 horses. Procedures—Data collected included signalment, history, intended use, duration and severity of lameness, results of diagnostic anesthesia, radiographic abnormalities, MRI abnormalities, and outcomes for return to use. Results—MRI was conducted on 23 horses with lameness localized to the foot. Thirteen horses had bilateral forelimb lameness, and 10 had unilateral forelimb lameness. Mean duration of lameness was 10.5 months. Seventeen of 23 (74%) horses had excellent outcomes and returned to intended use within 2 to 4 weeks after navicular bursa injection. Hyaluronate treatment was not associated with outcome; however, horses receiving < 10 mg of trimacinolone had significantly worse outcomes than those treated with hyaluronate. Among horses with excellent outcomes, mean duration of soundness was 7.3 months. Seven of 8 horses with erosive lesions of the flexor surface of the distal sesamoid (navicular) bone diagnosed via MRI had a poor outcome. Horses with navicular bursitis responded optimally to injection, compared with horses with other problems. Conclusions and Clinical Relevance—Results suggested that intrathecal injection of corticosteroid in horses with erosions of the flexor surface of the navicular bone associated with deep digital flexor tendon adhesions yielded a poor response. Treatment of horses with navicular bursitis via injection of the navicular bursa should be highly effective in alleviating lameness.