Master of Science (MS)


Biomedical and Veterinary Medical Sciences - Veterinary Clinical Sciences

Document Type



There is anecdotal documentation that intra-articular administration of liquid silicone is used as a lubricant for equine joints. Effects of silicone polymer on equine articular cartilage and synovial fluid have not been evaluated. The objectives were to characterize the effects of intra-articular administration of liquid silicone polymer on clinical, synovial fluid, and microscopic features in normal middle carpal joints of horses, and to determine if silicone migrates to the axillary lymph nodes. Eight adult horses were used in this study. Two mLs of 1,000 centistoke, medical-grade silicone was injected into one randomly selected middle carpal joint. The opposite middle carpal joint was injected with two mLs of 0.9% NaCl. Degree of effusion, range of motion, pain on flexion, joint circumference, and degree of lameness were determined prior to injection, at 2, 8, 12, 24, 48, and 72 hours after injection, and weekly for 6 weeks after injection. Radiographic examination, synovial fluid analysis, and microscopic examination of synovium, articular cartilage and axillary lymph nodes were performed at the conclusion of the study. Joint circumference for silicone-treated carpi was significantly greater (p < 0.05) than saline-treated carpi from eight to 336 hours after injection. There was a significant association between treated limbs and lameness, lameness after flexion, pain elecited upon maximal flexion of carpus and middle carpal effusion in treated limbs. Radiographic examination did not reveal the presence of osseous abnormalities; however, effusion was present in 4/8 silicone-treated carpi and 2/8 saline-treated carpi. Synovial fluid from silicone-treated and saline-treated carpi had normal protein concentrations and total nucleated cell counts. Synovial fluid from 5/8 silicone-treated carpi had refractile cytoplasmic vacuoles within macrophages. All silicone-treated carpi had synovial hypertrophy with 7/8 silicone-treated carpi demonstrating accumulation of vacuolated cells containing silicone. Examination of articular cartilage from saline-treated and silicone-treated carpi did not reveal a significant difference. Silicone was not definitively demonstrated in any axillary lymph nodes. Administration of silicone into the middle carpal joint resulted in synovitis. A single administration of silicone polymer had no apparent effects on articular cartilage within six weeks of administration.



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Committee Chair

Daniel J. Burba